2005, Sarah Hartwell


In the 'pre-genetics' era there were several theories about inheritance. Some were based on misinterpretation of observations and some on wishful thinking. The female cat's ability to mate with multiple males and produce kittens with different fathers further confused the matter - it is harder to spot trends when half the kittens were fathered by the tomcat you didn't see mating with your female!

According to the theory of 'Maternal Impression', the unborn offspring were affected by the mother's environment. The female could, therefore, be mated to a mediocre stud, but if the pregnant female was then housed in close proximity to outstanding examples of her own species, the sight of those animals would cause her to impress their characteristics onto her unborn young. On the other hand, if the pregnant mother was exposed to a bad example, that would be transmitted to her offspring. This led to some unusual advice on mating and housing cats.

Paternal Impression (Telegony) claimed that a female's first ever mate had a permanent effect on her and would affect all of her future offspring, even those fathered by different males. If hers first ever mate was an outstanding stud, that stud's characteristics would supposedly turn up in later litters fathered by other studs. Breeders claimed to discern this influence, whether desirable or not, demonstrating the power of belief! Unfortunately, paternal impression meant that if an female animal was mis-mated to a poor quality on moggy male she was "ruined for life" and would always produce tainted poor quality offspring. Many such females were needlessly destroyed. One Persian female who had "strayed from the path of virtue" apparently had only poor quality kittens from a good sire, "what might be called half-breeds".

Paternal Impression in dogs, cats, horses and sheep was described in "Anomalies and Curiosities of Medicine" (1896) by George M Gould and Walter L Pyle. "The influence of the paternal seed on the physical and mental constitution of the child is well known. To designate this condition, Telegony is the Word that was coined by Weismann in his "Das Keimplasma," and he defines it as "Infection of the Germ," and, at another time, as " Those doubtful instances in which the offspring is said to resemble, not the father, but an early mate of the mother [...] Hon. Henry Scott says [...] I have a cat now which appears to be half Persian (long hair). His dam has very long hair and every appearance of being a half Persian, whereas neither have really any Persian blood, as far as I know, but the grand-dam (a very smooth-haired cat) had several litters by a half-Persian tom-cat, and all her produce since have showed the influence retained. The Persian tom-cat died many years ago, and was the only one in the district, so, although I cannot be absolutely positive, I think this case is really as stated." Unknown to those early authors, longhair is carried as a recessive (hidden) gene in cats and the later longhaired kittens would have resulted from inbreeding.

Sometimes Paternal Impression is distinguished from Telegony and defined more in line with Lamarckism, being the inheritance of traits acquired by the sire during the sire's lifetime. For example, if the male lost an eye through injury, his offspring are likely to be born with one eye or have one eye blind or deformed. Likewise Maternal Impression could be defined as inheritance of traits acquired during the mother's lifetime rather than environmental factors impressed upon her unborn kittens.

Lamarckism, and 18th Century theory, stated that characteristics inherited during an individual's own lifetime would be transmitted to the offspring. During their lifetime, individuals would lose characteristics they do not require and develop characteristics that are useful and heritable. Hence the Manx cat supposedly resulted from cats whose tails had been amputated. Lamarckism was revisited in the 1930 in the form of Lysenkoism.

Mendel's theory of dominant and recessive genes was published in 1865, but the knowledge remained in the realm of scientists and was not widespread in the British livestock fancy until probably the 1930s. Into the early 1900s, breeders still relied on their own observations and conclusions. One theory was "mixing" or "blending" which had some basis in observation: offspring inherited a mix of traits from the parents. Breeders therefore assumed that breeding black cats to white cats resulted in grey cats and sometimes it did give grey cats due to the recessive dilution factor. That the blending theory often worked when trying to brighten tones in tabbies would have been due to polygenes. Throwbacks were also recognised although the mechanism (recessive genes) wasn't understood. This made early attempts at selective breeding somewhat hit or miss.

There were no texts equivalent to our modern genetics text at this time, but plenty was written on how to breed cats and those essays, letters and books illustrate early beliefs on inheritance. From the 1880s, it was also generally believed that cats were becoming weaker than their predecessors. This was blamed in part on the breeding of delicate pedigree cats, especially imported varieties such as Angoras, which supposedly brought disease with them. The belief was probably fallacy, though inbreeding and poor diet may have weakened some cats. A female mated towards the end of her season would supposedly have male kittens. If the stud cat was fed well, rested and strong before mating, females would predominate in his bride's litter.

Mr. St. George Mivart gave mentioned the belief in Lamarckism in his book "The Cat" (1881). He mentioned a case where a female cat had her tail badly injured when a cart-wheel ran over it and the owner judged it best to amputate the whole tail. Since then, the female had had two litters of kittens, and in each litter some of the kittens had a stump of tail, while the others had full-length tails. However it was possible that there were Manx cats in the neighbourhood. Mivart considered the claim analogous to that of a breed of short-tailed sheep-dog apparently produced from parents whose tails were amputated. Harrison Weir, in 1889, was sceptical of the claim, noting that sheep - whose tails were routinely docked - did not have short-tailed or tailless lambs.

Weir also wrote that cross-breeding Manx with other cats often resulted in tailless offspring, citing the case of Mr Herbert Young of Harrogate, whose "very fine red female long-haired tailless cat was the offspring of a Manx and a Persian". Another case which showed the strong prepotency of the Manx was Mr. Hodgkin of Eridge whose Manx female produced tailless cats when crossed with an ordinary domestic cat, and whose offspring themselves produced some tailless kittens. One of the earliest scientific studies into Manx inheritance appeared in the German paper "Mutter Erde" and then in "Our Cats" in March 1900. It clearly described the dominant nature of the Manx gene:

"The Progeny of a Tailless Cat of the Isle of Man. A cat brought from the Idle of Man (felis catus anura) to S. Germaine en Laye, of which the pedigree is unknown, was mated with ordinary long-tailed cats, and among twenty-four kittens, the four following kinds appeared:

I - Kittens with ordinary long tails.
II - Kittens with short and stump tails.

III - Kittens without tails, like the mother.
IV - Kittens without the least sign of a tail.

The comparison between the influence of the sire and that of the dam on the young is interesting:-

1 litter - 1 kitten like the mother.
2 litter - 6 kittens, 5 like the mother, 1 like the father.
3 litter - 5 kittens, 3 like the mother, 2 like the father.

4 litter - 3 kittens, 1 like the mother, 2 like the father.
5 litter - 4 kittens, 1 like the mother, 3 like the father.
6 litter - 5 kittens, 3 like the mother, 2 like the father.

It will be seen that the influence of the mother predominates."

In 1900, an anonymous writer in "Our Cats" observed that Manx may have originated as sports that were perpetuated as curiosities, much like sports in dogs and fowl. However, breeder, fancier and author Mr H C Brooke gave some credence to Lamarckism when he wrote "What is the origin of the Manx? That is a question which in all probability will never be answered. The theory that it originated from a cat (or cats) having lost its tail by accident I do not consider worth a moment's considerations. Such a cat might well have tailless progeny, but that would have nothing to do with the abnormal length of the hind legs, which in good specimens is patent to the most superficial observer"

One of the first books to discuss cat breeding in any great depth was "The Book of the Cat" edited by Frances Simpson. Simpson advocated mating "pure-bred" cats (i.e. from like-to-like matings), not just "pedigree" cats. She advocated 3 generations of blue-to-blue breeding in order to produce "purebred" blue Persians. The book contained a whole chapter about colour breeding by Hester Cochran; this was based on observation, although the conclusions were not always correct and Mendelism was not applied. Pedigree records were not always accurate (cats could be renamed and reregistered) and some females were mated to 2 studs, making paternity uncertain. The following is distilled from contributors to Simpson's book.

The need for selective breeding was recognised, although the mechanism was not understood - Mendel's theories had not filtered through into the cat fancy. Inbreeding was considered a subject too experimental and speculative for there to be hard and fast rules. The generally accepted rule about inbreeding was 'once in, twice out'. Sometimes two excellent animals produced only progeny and breeders were advised to study the weak points of the dam and to select a stud that compensated for those weaknesses. Examining the pedigree would reduce the risks of throwbacks to other colours. Excessive inbreeding had caused chinchillas ('silvers') to deteriorate and all inbreeding was to be avoided until a stronger race of silver cats was established.

On the other hand, Mr Mason, a judge in the early 1900s said of inbreeding "I know a great many breeders are not in favour of this in-breeding. This is, without doubt, their loss. In all branches in-breeding is the sure road to success." Mason advocated inbreeding rather than outbreeding: "To go outside at every cross, or too often, brings with it a lot of trouble and disappointment. To all my advice is, having got the strains of noted sires in your youngsters, so mix them that all the good and little of the bad points will come out as the result of your breeding. That you will not get all winners is a sure conclusion, but my experience is - and it is formed after thirty years' breeding of fancy pet stock - that in this way you are more likely than in any other to breed winners."

It was recognised that outcrossing could improve type, but at the risk of introducing faults such as white spots, pale chins and wrong eye colours. It was realised that some of these faults might lay dormant for generations. According to Mason "All this proves that the breeders at times go too far in the outcrossing, and bring in with it faults that crop up when those crossings are nearly forgotten."

Lack of scientific breeding - outcrossing followed by inbreeding - caused the loss of the Mexican Hairless in the early 1900s. When the male was killed by dogs, the owner sought another specimen to mate with the surviving female. He was unsuccessful and the breed was lost, unnecessarily so since she could have been bred to a shorthair cat and the trait restored by back-crossing. Livestock breeders knew the value of back-crossing and the Edwardian breeders clearly understood the value of judicious inbreeding, but this knowledge was evidently not sufficiently widespread.

Many cat fanciers lacked the patience to follow colour breeding practices to a satisfactory conclusion. They were frustrated by "sports" and "throwbacks" because they did not know about recessive genes or polygenes and did not always study pedigrees before selecting mates. The ancestors had to be taken into account. "When breeding chinchillas, if we used a black bred from a brown tabby mother the results would be disastrous" (Cochran). Simpson wrote of the importance of pedigrees when breeding silver tabbies "Here comes in the study of pedigree. It by no means follows that the mating of two tabby parents will result in a litter of pure tabby kittens, unless both sire and dam and of pure silver tabby lineage. Here purity of pedigree on both sides is of great importance. If there is a trace of chinchilla blood in the ancestry it is certain to manifest itself at odd times in the progeny. Nevertheless, do not despise your shaded silver, if it be a queen, providing all other points are perfect [...] 'You no longer have a show specimen, but you have a cat that, crossed with a heavily marked cat, will provide you with splendid silver tabbies.' This, however, can scarcely be called the true science of breeding, as the progeny of two such cats may hark back to some of the original characteristics. My own practice is to mate silver tabby with silver tabby invariably, and of the purest pedigree I can find. I should never breed from a sire that I knew possessed a brown tabby ancestry. I would far rather choose a good black sire, and in this way strengthen the markings."

Cochran advocated the scientific approach to breeding for certain traits though there was still widespread belief in mixing (mating black to white to get grey; mating grey to white to get lighter grey) and some breeders still believed in paternal impression. Cochran had no doubt that judicious cross-breeding would produce new colours as she had already seen a chocolate-brown cat and also a yellow cat with black stripes (probably a golden tabby). She believed that careful cross-breeding could produce Dalmation-spotted cats and cats with zebra-stripes. Some of the aims were impossible. Breeders were hampered because some colours were considered unfortunate by-products of breeding programmes and their importance as gene carriers was not realised. Others had clearly recognised the occurrence of throwbacks and were trying to use this, for example one breeder wanted to produce blue-eyed orange cats by mating an orange female (sired by a blue-eyed white male) with a blue-eyed white male (her theory was actually sound, but she did not realise that blue eyes are tied to the white colour).

Cat fanciers were aware that there was a relationship between black and blue, red and cream/fawn (dilution) even they did not fully understand the mechanism and failed to use it to their advantage. Only a few colours and patterns were acceptable for exhibition and the others were often discarded or destroyed, their importance as carriers of traits not being recognised. Different breeders ahd different, and sometimes contradictory, views and methods.

Crossing whites with other colours was undesirable because it risked introducing coloured patches and smudges and undesirable eye colours. There was no knowledge of the 2 types of white cat - dominant (epistatic) white and white spotting - both of which could wholly mask another colour. Blacks were more troublesome as some turned out smoky or dirty (probably unrecognised dark smokes rather than self blacks), but it was recognised that a rusty black kitten was more likely to grow into a good black cat than a smoky black kitten. Crossing a black to a blue, smoke or silver was undesirable in most cases as the silver would pass on green eyes. Good blacks could be obtained from crosses to tortoiseshells or to red tabbies (the sex-linked orange gene had a lot to do with this) and the best blacks came from bright clear-coloured cats, not from dull colours such as smokes, blues and fawns. It was preferable to have blacks bred from silver tabbies than from dark brown tabbies, while a brightly coloured tortoiseshell supposedly threw the best blacks of all. The brightening effect were probably due to polygenes.

In 1889, Weir wrote that blue in cats was a mixture of black and white (as in mixing paint) which was all the more curious because black mated with white generally produced self blacks, self whites or black-and-white bicolours, but rarely produced blues. Blue was a "weakened" black whose exact shade depended on the colour of the black from which it was bred. There was a range of tint and tone from dark blue-black, through dark grey to a very light, almost white grey. To breed self blues, black-and-white parti-colours must be excluded from the breeding programme. Weir had evidently observed both the dominant (epistatic) self white gene and also the white spotting gene. Grey is, indeed, a weakened form of black, caused not by mixing with white, but by a dilution gene.

According to Simpson's contributors, blues should not be crossed with any other colour as there were so many different blue strains. However, another breeder stated that crossing blacks with blues gave tone, soundness and lustre to both the blue and the black offspring. Cochran found no truth in the belief that crossing a blue with a white would produce very pale blue kittens. Even without knowledge of the dilution factor, she wrote that crossing a black with a white might never produce any blue kittens, however many kittens they produced. While breeders had noticed that some black cats produced blue offspring, they concluded that this effect was related to gender and that the black parent should be the male otherwise the kittens would very likely all be black. Mr Mason advised those who bred self blues or self blacks to put one cross of blacks in the blues in order to get good eye colour into the blues. He cautioned that mixing those colours too often would result in blues too dark or nearly like black (the "mixing" theory). The kittens from a blue to black mating should be bred together, though many breeders were not in favour of this sort of inbreeding.

The (black) smoke had been crossed with self blacks, silver tabbies and blues. Cochran noticed a close affinity between the smoke and the silver tabby and stated that they should not be crossed because of unwanted facial markings (probably shaded silvers); she recommended judicious crosses of black, blue or (best of all) chinchilla (she did not realise that this would also introduce tabby markings). The black cross was preferred over the blue because it would intensify the black mask (though either cross endangered the undercoat). A blue cross quickly helped to eliminate markings; but the blue kittens were to be discarded as their colour would never be satisfactory (they were often blue smokes or produced blue smokes).

The best crosses for a chinchilla were, in order of preference, the smoke, then the black, then the white. Crossing the chinchilla with a white produced a dingy, dirty white cat (no doubt due to whatever colour the white was masking resulting in unrecognised tipped colours), which was unattractive, but could be crossed with a chinchilla, a black or even a blue. Blue chinchillas were undesirable ("muddy, dull colour"). Cochran had noticed a link between chinchilla and tabby, but again concluded that this was due to the gender of the blue parent; if the blue parent was the female the mating would produce blue tabbies.

The close relationship between chinchilla and silver tabby was not understood. Chinchilla kittens occasionally turned up unexpectedly, for example in a litter sired by a cream male (of brown tabby and cream parentage) on a pale blue female (of blue and a blue tabby parents). "There may have been silver tabby blood in the strain, but certainly no chinchilla." It was known that some excellent chinchillas, from chinchilla parents, produced only brown tabby kittens, however they were mated. A well-known breeder of silvers says: "Although it may be incorrect to cross silvers and browns, it is often most successful".

There were two types of brown tabby - the brown tabby and the magnificent "sable" (probably golden tabby or shaded golden) which was considered not really a tabby. To counter the tendency for over-heavy markings in brown tabbies, breeders were advised to outcross to a strongly marked red tabby to brighten the colour. After mating to another colour, there was a danger of the colours "washing out" (the effects of polygenes), though the brown tabbies were less prone to this than the silver tabbies (tarnishing). Another breeder contradicted this and wrote that the old brown tabby should be crossed with the sable tabby and that blending together those two colours will put any breeder on the highway to success. Breeders also noticed that brown tabbies bred together sometimes produced good black kittens (now known to be the recessive non-agouti gene).

Cochran remarked that she had bred beautifully marked clear silver tabbies from a brown tabby sire and a sandy, silver tabby female, both of unknown pedigree. However Mr Mason wrote that it was a great mistake to cross the silver tabby with either a brown tabby or with a silver that had brown tabby ancestors. To intensify black markings, he recommended a once-only cross with the self black. If the desired effect did not result from the first cross, the kittens should be bred together to produce silver tabbies. Crossing the brown tabby with an orange was recommended to produce a brighter tone, but not all breeders reported good results. Mating self blues to brown tabbies produced blue tabbies and, if lucky, good blues. Crossing a brown tabby cross with a chinchilla produced good brown tabbies and equally pure silvers, although breeders often avoided the cross as they thought it would give silvers would be tinged with brown or streaked.

Without the knowledge that the non-agouti gene does not affect red pigment, breeders were attempting to produce true self reds, but were unable to eliminate the facial markings. They were advised to cross their self-reds to blue cats to overcome the problem of facial markings, but at the risk of producing dull yellows and fawns. The almost vanished red tabby could be restored by crossing a brown tabby with an orange. Just as blue is now known to be the dilute of black, cream is the dilute of red. Other genes make reds and creams richer or paler in colour. In 1903, "red" referred to the richer colour while others were "orange". Cream was described as a pale, yellow. There were also "fawns" ("biscuit" or "hot" creams) which were considered quite separate things even though they appeared in the same litter. Clear, pale yellow creams could be bred from oranges and tortoiseshells. The more easily produced fawns and creams were considered a fault of their ancestors.

It was known that a cross of blue and orange often produced fawn kittens, especially if the dam was blue. When the dam was orange or tortoiseshell there would often be worthless blue tortoiseshell kittens. Because creams had become inbred, breeders were encouraged to cross cream females to blue males, resulting in cream and blue-cream offspring. The blue-cream offspring should not be discarded, but should be bred to a cream male to get good cream-colour kittens. Other breeders considered the blue-creams "impure" and would only breed creams from the more valuable orange/black tortoiseshells. In fact tortoiseshells were reputed to be able to produce almost any colour and could be mated to blue, cream, smoke or chinchilla males to produce blacks, blues, creams, oranges, fawns, smokes and chinchillas respectively. Much depended on how the tortoiseshell female herself had been bred (in modern terms - carried recessives).

The best tortoiseshells were bred from a black mated to a red tabby or orange. A tortoiseshell mated to a black-and-white produced tortoiseshell-and-whites. Red tabbies were avoided in producing tortoiseshell-and-whites because of the red tabby markings. The lack of tortoiseshell males, in spite of attempts to selectively breed them, was recognised and the orange male was - correctly - considered to be the male of the tortie breed. Miss M Beal wrote of the tortoiseshell: "One curious fact in connection with long-haired tortoiseshells, which is well-known to fanciers, may be mentioned, namely, the non-existence of the male sex. Among short-haired tortoiseshells toms are exceedingly rare, though one or two do exist, but an adult long-haired male appears to be absolutely unheard of. The writer knows of one male kitten born some years ago, but it was either born dead or died in very early infancy. Darwin's theory that the orange tom and tortoiseshell queen were originally the male and female of the same variety is borne out by the fact that until recently orange females were also rare. Of late years a good many of these have been bred and reared, and therefore, if the Darwinian theory be correct, it seems hard to believe that the tortoiseshell tom must be regarded as unattainable. If the difficulty has been successfully overcome in the one case, why not in the other? Breeding with this object in view is very slow work, for some tortoiseshell queens will produce litter after litter without a single kitten of their own colour, and a family consisting entirely of tortoiseshells would be as welcome as it is rare." In 1881, Mivart had also written that the sandy tom cat was the male of the breed of which the tortoiseshell was the female.

In the breeding of orange tabbies, the use of the tortoiseshell was found to have produced some of the best orange tabbies and also good torties. Mason wrote "care should be taken not to bring too much of the tortoiseshell into the orange, or, on the other hand, carry too much orange into the tortoiseshell". Others noted that crossing an orange male with a cream female resulted in sound coloured specimens of both sexes and varieties. A blue male and a tortoiseshell queen would produce good orange offspring (though seldom of the female sex) though mating tortoiseshell and orange together produced mostly black kittens and rarely ever an orange female. Another wrote that crosses between orange and a tortoiseshell they often got blacks and blues as well as oranges; a cross between blue and a tortoiseshell could produce an orange.

Breeders had also noticed the ratio of colours produced when mating an orange male to either a black or a tortie female: "An orange stud cat is a very useful animal to have in a cattery, for crossing with him will improve many colours, viz. Tortoiseshell, brown, grey, and sable tabbies; while if he is mated to a blue queen the kittens, if orange, are beautiful in colour - brighter, I think, than if two orange cats are mated together. In mating with other colours it is a toss-up what colour will predominate, but the only way to ensure all orange kittens is to mate with orange queens, when, according to my experience with my stud cat ('Torrington Sunnysides'), the results are all orange. Mated with tortoiseshells the orange kittens are very good; but mated with blacks the strongest colour carries the day, and the kittens are mostly black or tortoiseshell, seldom orange. Silvers, chinchillas, and smokes should of course never be mated with oranges, as the result would be a horrible mixture!"

One of the first discussions of tortoiseshell inheritance, including tortie tomcats, was by L Doncaster in 1905 and is mentioned in Experimental Zoology (Publ. Macmillan & Co, London, 1910) by Thomas Hunt Morgan (Professor of Experimental Zoology, Columbia University). Although this discusses tortie in general, it is reproduced in full as it draws conclusions about tortie toms. Dominant and recessive traits were understood, but sex-linked traits were not and the orange male was erroneously believed to carry black as a recessive colour.

Doncaster [Doncaster, L. On the Inheritance of Tortoiseshell and Related Colours in Cats. Proc. Cambridge Phil. Soc. XIII. 1905] has brought together a number of records, obtained from owners of pedigree cats, that show the color inheritance of certain breeds. He examined more especially the question as to why tortoiseshell cats are nearly always females. His conclusions, as will be seen, have an important bearing on the problem of dominance in relation to sex. Tortoiseshell kittens may be obtained in any of the following matings : -
(a) Tortoiseshell F by tortoiseshell M
(b) Tortoiseshell F by black or blue M
(c) Tortoiseshell F by orange M
(d) Orange F by orange M
(e) Orange F by black or blue M
(f) Black or blue F by orange M

In all of these matings, in addition to tortoiseshell, kittens of other colors may appear, viz. :-
(a) Tortoiseshell F by tortoiseshell M gives tort, orange, black.
(b) Tortoiseshell F by black or blue M gives tort. F, orange M , black M & F .
(c) Tortoiseshell F by orange M gives tort., orange, black.
(d) Orange F by orange M gives either tort., orange (or blue) or only orange.
(e) Orange F by black M gives tort. F, , orange M .
(f) Black F by orange M gives tort., black (and probably orange).
(g) Black F by black M gives only black (or blue).

From these results it appears that tortoiseshell is a heterozygous color produced by the meeting of orange and black gametes. The explanation that tortoiseshell cats are nearly always females and rarely males is owing to orange nearly always dominating in the male over black, while in the female the dominance of the orange is incomplete, so that tortoiseshell results. In other words, in the female sex the orange and the black both exist together, while in the male sex the yellow usually dominates. A few examples will make the conclusion clearer. For instance, in mating (e) when an orange female is crossed with a black male, only tortoiseshell and orange kittens are produced; if both the orange and the black breeds are "pure," the female offspring are tortoiseshell and the males yellow. In the reverse mating (f), where a black female is crossed with a male orange, the male may be heterozygous (i.e. having both black and orange germ-cells), hence black kittens may also be produced. The kittens will be black males or females, tortoiseshell females, and orange males.

When a tortoiseshell female is mated with a black male, the male offspring will be orange, because the tortoiseshell is heterozygous. It is also evident why orange females are very rare, although orange males are common, since in all matings in which one of the parents is black, orange can appear only in the male offspring. "If, therefore, the great majority of orange males contain recessive black, when they are paired with tortoiseshells, only a quarter of the kittens will be pure orange, and only half of these females."

The preceding statements show the relation of the colors orange and black. The inheritance of two other colors was also examined ; namely, cream and blue. Cream appears to be a dilute form of orange, and blue of black. The blues breed true (when derived from yellow ancestors) and are therefore recessives or homozygous. A cream female and a blue male give blue tortoiseshell (blue and cream), cream males, but no blues, since the cream dominates incompletely in the female, completely in the males. On the other hand, a blue female and a cream male give blue tortoiseshell females, blues of both sexes, and possibly cream males. These and other results show that the dilute forms behave in the same way as do the stronger colors. Thus cream is dominant over blue in the male, but when blue and cream meet in the female a tortoiseshell results.

It has been stated that male tortoiseshell cats are known, although they are rare. It must be assumed that in such cases the dominance of the yellow is incomplete as in the female. This means that while complete dominance is usually associated with the male character, it is not necessarily always associated with this sex. It is interesting: to find that when a male tortoiseshell is mated with a female of the same color, the kittens are tortoiseshell, orange, and black. This is what is expected on the assumption that the germ-cells of the tortoiseshell are black and orange (with the alternate character latent on my view). The prepotency of different tortoiseshell individuals (males) seems, however, to vary.

Some cream-to-cream matings also produced unwanted orange-and-creams (the latter would be cream tabbies). The rarity of cream females resulted in advice to breed from a nondescript coloured female (blue-and-cream, tabby, tortoiseshell, or anything that had cream or orange about it). Creams also appeared as freaks in other colours - silvers, tabbies, etc.

Understanding inheritance was complicated by the fact that breeders did not always correctly identify the colours and sometimes mismated their cats. In the 1890s, some supposedly blue cats turned out to be smokes! Smokes arose from crossing of blues, blacks, and silvers, and appeared as freaks in litters of blues or silver.

Crossing smoke queens to black sires apparently gave good smoke kittens. Crossing them to blue sires gave a mixed litter of blacks and blues. Crossing blue queens to black smoke sires gave chiefly blacks. However many apparently smoke kittens developed tabby markings, showing traces of the far-away silver tabby ancestors. One breeder correctly remarked that the markings had been lying dormant for a generation, and appeared as a reminder of the silver tabby origin of the smoke. Without knowing it, breeders perpetuated tabby markings by recommendation to mate overly dark smoke queens to chinchilla (silver) males produce lighter smoke kittens. Dark smokes were in vogue in England, but light smokes were the rule in America. It was considered better to be on the safe side and breed for darker smokes, as the lighter smokes could overstep the line that divided them from shaded silver. Much later, it would be understood that smokes are non-agouti, while the shaded silver and chinchilla have the agouti factor.

There was a habit of mating smoke queens with any coloured cat which took a breeder's fancy in the hopes of getting something in the litter besides smokes. The supposedly smoke females from those matings often failed to produce any smokes themselves when mated to a smoke male and instead produced throwbacks to their own coloured sire. There was certainly the recognition of recessive traits, even if there were no terms for this apart from "throwback". Blues were avoided as the undercoat apparently became bluish.


Choose your sire most prayerfully,
And treat your queen quite carefully,
'cause the kit will be what they have been,
You can't escape your kith and kin!
Advice to breeders in the early 1950s.

As late as 1958, PM Soderberg took pains to dispel the myth of telegony ("Pedigree Cats: Their Varieties, Breeding and Exhibition"): "Unfortunately, in the now distant past a large number of queens were destroyed because telegony was accepted as a fact instead of being, as is actually the case, sheer nonsense. Despite the stupidity of the belief, even now from time to time the same old story is brought out for the acceptance of the ignorant. Fortunately, the vast majority of breeders, however, now know that there is no truth in this myth. When a queen has been mated and kittens have resulted, the very act of giving birth removes from the body of the female all trace of her association with the particular male which by choice of selection happened, or even by accident happened, to be the father of her progeny. The male can only influence kittens resulting from the sperms which he emits, and those which are not actually used for the fertilization of the ova very quickly die. It has been stated on more than one occasion that sperms can remain alive for as long as seventeen days in the body of the female, but even if this is the case, it means that there will be none left even three weeks after the last mating has taken place. Thus, as the period of gestation is nearly three times as long as this, there can be no possibility that any sperms will be alive to affect any future litter of kittens. The absorption of seminal fluid may have certain other physical effects on the female, but this is entirely another matter. Telegony must be regarded as just one of those old wives’ tales which seem to continue their existence just because they are so ridiculous and lacking in any scientific basis."

In 1955, Albert C Jude had published the first detailed volume on cat genetics. He also contributed a detailed section on "Scientific Breeding" to PM Soderberg's "Pedigree Cats: Their Varieties, Breeding and Exhibition" (1958). Much of these were given over to explaining the roles of eggs, sperm, gamets, zygotes and chromosomes and basic Mendelian inheritance. The concepts of dominant, recessive and epistatic genes and of homozygous and heterozygous cats are familiar to modern cat breeders, but were quite revolutionary to Jude's audience (if you are unfamiliar with these concepts/terms, there are plenty of websites that give a beginner's guide to genetics). Inbreeding, line-breeding and hybridisation were more familiar, but not the reasons why or how such practices worked or failed.

Jude wrote that in its simplest sense, "breeding" meant sexual reproduction and survival of those progeny most capable of perpetuating the species. In the hands of the animal fancier, "breeding" meant selecting parents whose offspring will satisfy the aesthetic outlook and whose colour and form comply with a predetermined breed standard. "Breeding" was hence both an art and a science and the more a breeder realized and understood the science, the more intelligent would be the choices and the more successful and satisfactory the outcome. Not all breeders embraced the new science of heredity, some older or established breeders clung to old beliefs.

In Jude's own words: "During the last few years cat breeders have become much more conscious of the importance of scientific principles as applied to breeding operations. Mode of inheritance and what it produces has become a scientific study, the results of which are there for the fancier to use to his advantage. But, even so, all this may be useless unless the breeder is able to interpret the facts and their meanings through the art of selection. Knowing how, but first knowing why, is a combination of much value in all walks of life, and not by any means least in fanciers’ controlled breeding methods. Even though more cat fanciers than ever are prepared to accept and apply the principles of heredity, there are still some who either fail to appreciate the significance, or who are so smugly satisfied with chance methods that they ignore or even reject the whole idea. Perhaps the trouble is that when scientific matters are suggested, all too often a feeling of ‘can’t be bothered’ or ‘I wouldn’t understand anyway’ comes about. This is the pity of the thing, for quite frankly all that is really necessary for the average fancier-breeder is the more elementary part of the subject, and this is so simple that once it has been tackled it becomes a real fascination. Certainly no breeder can afford to miss the usefulness or the added interest which can be derived from such a small amount of study as is needed."

Jude broke in his audience gently by saying that even novices with no previous experience of animal breeding or heredity would select those animals that apeared to be suitable pairs. This suggested an instinctive knowledge that like begets like and that the parents should complement each other in order to have superior offspring, perhaps one parent having a strength where the other had a fault. This meant that even novices instinctively grasped that there were rules governing the orderly transmission of characteristics: "Therefore, is it too much to ask that these breeders will acquaint themselves with the ‘whys’ and ‘wherefores’ rather than turn the deaf ear which they so often seem to do?" The idea of rejecting genetics seems odd to 21st century cat breeders, most of whom have at least a basic understanding of genetics and many of whom have "Robinson's Genetics for Cat Breeders" in their personal library!

Jude admitted that until recently (1940s and 1950s), few people had given any though as to how parents passed on traits to their offspring and even fewer had made a detailed study of the matter: "Obviously for centuries man must have more or less consciously attempted to improve his domesticated races of animals and plants, yet there is a complete lack of evidence that he even tried to unravel the complexities of heredity. It would seem that until the time of Aristotle the production of offspring in animal life was held to be similar to the production of a crop from seed. It was apparently assumed that the seed came from the male, and that the female was nothing more than the equivalent of soil in which the seed would grow. This was the generally accepted idea for a great length of time, and it was not until the advent of the microscope, which then made possible actual observation of the minute sexual cells, that the physical basis of heredity became established. Research into the problems revealed lasted through a century, and finally, by the end of the eighteenth century, the scientists became agreed on the view that each of the sexes makes a definite material contribution to the offspring produced by their joint efforts - the female contributing the ovum, and the male the spermatozoon."

He explained that, except for rare instances of parthenogenesis, each new individual was the joint product of both the male and female parent. Factors (an old term for what we now call genes) for form, colour and health, whether for good or for bad, were brought together from the chosen parents to be embodied in a new individual. It is finally the will and discretion of the fancier in choosing which cats to mate together which were important. He gave the example of following the inheritance of traits when different cat breeds were crossed: characters such as long or short hair, large or small ears, long or short tail were all due to genes located on chromosomes carried in the nucleus of the germ cells - "This is the theory which is known as the theory of heredity, or the theory of the gene." He added that the way in which these characters were transmitted conformed with Mendel's law and depended on differences between pairs or a series of genes, though he later went on to introduce the concept of modifying factors where intermediate types were produced, rather than simple Mendelian dominant/recessive characteristics.

Jude listed the 10 known gene mutations of the cat of interest to the 1950s cat breeder. These differ from modern listings as he incorrectly believed silver to be part of the Siamese albino series and Rex to be an alternative to longhair or shorthair.

1. Lined tabby (tL), mackerel tabby (+ [denoted 'wild-type]), blotched tabby (tb), black (non-agouti, a).
2. Black (of Siamese, B), tabby.
3. Black (+), yellow (sex-linked, y). Heterozygotes tortoiseshell (+/y).
4. Intense, dilute (blue, cream).
5. Full colour, silver (CCh), Burmese (Cb), Siamese (Cs) (an albino series).
6. Coat white (eyes coloured, W), coat coloured.
7. Unspotted, piebald (white spotting, S).
8. Short hair, long hair, Rex.
9. Short tail (Manx), normal tail. Homozygotes tailless.
10. Polydactyl, normal toes.

He noted that there were other mutations less likely to interest the breeder. In the main, the interesting mutations were those concerned with colour. Variations in feline coat type in were restricted compared with those seen in dogs and, in general, breeders were only concerned with hair length although a rex mutation had occurred in 1952. This was reported in Nature, July 11th, 1953 by AC Jude, and a full description and report, including the results of experimental breeding tests, was being prepared for the Journal of Genetics by Jude in conjunction with AG Searle. Since cat breeders would be unfamiliar with the rex fur type, he described it with reference to mice and rabbits, but stated that the object of rex cat breeders would be to produce selectively the type of coat characteristic of the rex rabbit - very short and very plush-like, without wave i.e. like velvet rather than the rex we see nowadays!

The main aim of the cat breeder was to produce an animal that conformed to its breed standard though this was never achieved in practice according to Jude. Even in the oldest and best-bred varieties, there were small differences between individuals, while in carelessly-or ignorantly-bred strains there might be even greater differences within a single litter. He defined "type" as a collection of features with only small variation between individuals, though even that small variation might be of considerable importance on the showbench - hence the importance of scientific principles in breeding.

To Jude, it was clear that only a few cases conformed to the simple Mendelian rule since intermediates occurred when crossing cats that had extreme differences in size, conformation or shade. Longhair and shorthair was a simple dominant/recessive relationship. However, if purebred longhairs were interbred, the resultant hair lengths included intermediates and the same applied when purebred shorthairs were interbred. The same applied to colours - in blue longhairs, breeders selected for a light even shade while in other colours they selected for dark shades. Jude had no exact answer for this, but suggested that 'modifying' genes altered the result to produce darker and lighter shades within a single colour. "The practical importance of this is that it is wrong to believe that outcrossing brings the improvement desired for this and like features in the best possible way, for although differences in shades are perceptible, the presence of the necessary modifying genes can only be known as a result of actual matings. It is, therefore, preferable and safer to keep ‘inside the breed’, and select for the desired improvement. Dominance of ‘dark’ shade over ‘light’ must not be misinterpreted. In effect, it means that if ‘darks’ and ‘lights’ were allowed to breed together freely, the ‘darks’ would eventually be the rule. In controlled breeding within a breed, one has to expect intermediates from the ‘dark’ to the ‘light’ matings, with a tendency to the dominant or incompletely dominant forms. In other words, it needs hard selection to produce and maintain the very light shade in the example quoted because the natural pull is to the ‘darks’. The same principles apply to other details of make-up such as ear sizes and shapes, eye sizes and shapes, skull widths and so on."

Many of the animals of the small livestock Fancy, including the cat, originated from a similar kind of wild coat-pattern with a three-colour content: black, brown and yellow. Jude wrote that these pigments were of 2 main types: melanin pigments and lipochrome pigments. "The melanin pigments are derived from the blood. They are waste products, deposited in the hair instead of being carried out of the system with the other waste materials. Black and dark brown are the most conspicuous of the three pigments. Yellow is a lipochrome or fat pigment, and is derived from the reserves of the body. All pigments found in cat hairs are protein derivatives." In albino and partial albino animals, he explained, some unidentified chemical substance necessary to the formation of pigment was either wholly lacking or present in very limited quantity. He viewed coloured-eyed white cats as a "near miss from albinos" and the fact that white was dominant in cats was also unusual when compared to many other small animals. He also explained that the white merely masked the cat's normal colour and that white cats could produced coloured offspring when mated to coloured cats. Prior to that, breeders had believed that crossing blue cats to white cats would lighten the shade.

New colours were, therefore, produced not through breeding existing colours, but through 'mutation', another novel concept for the 1950s breeder. "A mutation then is an unexpected result which comes from a mating which normally gives only certain definite characters, and no others. The reason why we do not see more of these novelties in wild state is because for environmental reasons they may be quite short-lived, and therefore do not get a chance to perpetuate. A mutation or brusque variation may arise suddenly, but may take centuries in the wild for the new strain to become a stable species or variety of the species. On the other hand, it is part of a biological education to go to any sort of small livestock show and note the many true-breeding varieties the fancier has established in a relatively short time, and to see that novelties are still emerging from time to time. But Nature holds the key, and it is not until she has loosed a variation that we are able, through a system of back-crossing and intercrossing, to perpetuate the new form, and use it according to our knowledge of colour inheritance to produce further fresh colour forms within the range of possibility."

When a desirable variant occurred, it was up to the breeder to match together similar variants to start a new strain. To create a stable strain he should eliminate undesirable factors, breed like to like and prevent intercrossing with other strains i.e. he should practice inbreeding. With Mendel's law to aid him, Jude stated that the breeder was able to work more rapidly than before to graft one good quality after another onto a promising stock i.e. artificial selection in place of natural selection. "It cannot be said that the fancier’s sifting and breeding methods are always attended with perfect success. Some of the breeds of animal that man has produced seem undesirable and semi-pathological products which Nature would do away with within a week. Some of these have been given accentuated characteristics - such as ultra-short noses in cats - and through this have become deformed, perhaps dull-witted, and, worst of all, probably non-viable. Or the introduction of some lethal or sublethal factor may damn a strain for ever. In some cases these things are done deliberately because they please a breeder or maybe satisfy his customers’ perverted taste. But these dysgenic products we are glad to forget when we see the large number of really fine animals the fancier has evolved. On the whole, we can say that cat breeding has been eugenic [...] Nothing which is produced and seems to the fancier ‘different’ or unusual should be passed over or discarded. Advice should be sought, for this something ‘new’ may prove to be a stepping-stone in a fancy to something both interesting and useful."

With fewer types in existence, colour-breeding was the absorbing interest for most cat fanciers. Other breeders condemned colour-breeding, especially in pursuit of a rare colour, as it all too often led to the sacrifice of more important points. Jude theorised that the first mutant form from the ancestral tabby was not white (albinism being a relatively common mutation in other species), but black i.e. loss of the tabby pattern (since melanism occurs in other species). More mutations were necessary to broaden the palette. "If animals of a well-established colour variety pair with others like themselves, they may breed true indefinitely; but if no care is taken, and if the pairing is promiscuous, there must be, sooner or later, a restoration of the original complexity of the wild coat colour-pattern. This is called reversion. Disappointments with well-established breeds are often due to undesired pairing with dissimilar forms." He gave an example of the use of genetics in colour breeding: the introduction of a new colour into the Siamese. "This is readily done by introducing the gene through crossing with any type that carries it. This suggestion of crossing with another breed does, at times, rather shock the pedigree purists. It was, however, used during the formative period of almost every breed, and it is entirely unscientific to refuse to utilize the simplest method of attaining what is required. The important thing is to know exactly what is wanted from the crossing, and to make only such matings as are necessary to attain that end." He viewed colour prediction as relatively simple as most breeds could, by that time, be considered homozygous for several factors.

Tabbies were classified as lined, striped and blotched, with dominance in that order. 'Lined' tabbies were described as having stripes quite close together except on legs and tail so that they appeared to be a uniform agouti (ticked) pattern with a dark vertebral line. This pattern had been cultivated into the Abyssinian breed. Searle, considered the striped (mackerel) tabby to be due to some variations of the normal lined pattern due to modifiers. The blotched (classic) tabby showed much variation in England and America according to Professor Haldane.

In addition to normal black (non-agouti), chocolate-black was recognised in Siamese and Burmese as being a separate colour found in association with either Siamese dilution or Burmese dilution (it is now considered to be the interaction of dilution with ordinary black). The silver gene was considered to be part of the Siamese/Burmese series, having the effect of removing yellow from the banded hair to produce silver tabbies and chinchillas (silver tabbies and chinchillas being due to slightly different CCh genes, according to Jude). According to Dr Spurway, the silver gene did not affect the yellow-coloured areas in tortoiseshell cats. Yellow was the 1950s term for sex-linked red and the sex-linkage was understood i.e. that tortie males rarely occurred and were genetic aberrations. The fact that the non-agouti gene had no effect on the yellow colour was also understood i.e. that solid, unmarked red was impossible (although in the 1960s, Fernand Mery would write that solid red must have 'lost'!).

The term 'sex-linked' could cause confusion - human premature baldness was often described as a sex-linked condition even though the gene was passed on by either male or female, but only manifested in males. This, explained Jude, was a 'sex-limited' condition, not a sex-linked one. A fully sex-linked condition meant that the gene was carried on either the X chromosome (so that a man could only transmit it to his daughters) or the Y chromosome (he could only transmit it to his sons). He also described the complicating factor of ‘partial sex-linkage’ where the genes are carried in the sex chromosome, but could pass over from X to Y or vice versa (the male can transmit it to both sons and daughters, but transmits to a preponderance of sons, or a preponderance of daughters, according to whether he got it from the grandfather or the grandmother). Presumably the terms were being misused by laymen and he saw the need to clarify them. The yellow gene was a true sex-linked gene and the rare tortie male was described thus: "The tortoiseshell male is very rare, and is nearly always sterile. It has been suggested, in the absence of a clear definition of the genetic constitution of the tortoiseshell male, that he is a genetically-determined female which, under the influence of male sex hormone from an embryo of the same litter, has become an intersex, hence his sterility. But - it is suggested - if the influence of male sex hormone is unusually strong, effective spermatogenesis may occur in the testes, with consequent fertility." Jude gave it his best shot, and in fairness to him, research into tortie males continues into the 21st century with intersex being only one of the causes and fertile tortie males being due to a different condition entirely (chimerism).

With scientific breeding now possible, lethal factors and genetically caused disease became of considerable concern to the breeder. A lethal was defined as one that, when homozygous, caused the death of the individual. "The big snag about many lethals is that they produce small effects when present in a single dose, which may be looked upon as being desirable characters, and, therefore, selected for. The cause of death is probably an inability of the organism to perform some of its vital functions in the absence of the normal allele of the mutant gene." A dominant (more properly a semi-dominant) lethal altered the phenotype when heterozygous, but killed it when homozygous, the classical example given by Jude being the miniature Dexter-Kerry breed of cattle. Homozygous Dexter-Kerries resulted in grossly deformed offspring (stillborn or aborted). "A lethal of cats in this category is seen in the Manx where the homozygous form eventually fails to survive after a few generations. There are other lethals in the cat which are obviously far more deadly. A recessive lethal is one where there is no observable effect when heterozygous, but which kills when homozygous, just as does the dominant lethal. Recessive lethals are not easy to detect in mammals because one has to deduce their existence from the absence of one-quarter of the offspring; and whereas it is easy to notice the absence of say one hundred flies among four hundred, it is not so easy to notice the absence of one-quarter of a litter of kittens. The question of lethals brings the suggestion that fanciers should keep detailed records of facts: what went right as well as what went wrong; who was the father and what age the mother was; how many previous pregnancies or abortions; what any monstrosities looked like; what time during gestation abortion occurred; the relationships between the mates, and so on—if one has a body of reliable data, nine-tenths of the problem may solve itself. We have much to learn about lethals of the cat." Jude noted the emergence of an interesting class of lethals - translocations and deletions of parts of chromosomes due to x-rays and atomic radiations (including atom bombs). If the relevance of this escapes you, his article was written around a decade after Hiroshima.

As to disease, Jude was referring to an inherited tendency or susceptibility to disease (he called it a developmental tendency, but the modern usage of developmental tend to mean non-genetic factors due to the way the embryo develops in the womb). A breeder might purchase a perfectly normal or healthy kitten that gave no sign that it carried a tendency for a particular disease. It may have bred several times and its genetic tendency may have spread far and wide within the breed before that animal finally exhibited any problems. This confirmed the importance of keeping good records. Jude also clarified the matter of a queen passing on disease to her kittens through her blood-stream or her milk - the diseases were not inherited in the true genetic sense. This sounds obvious today, but was less so to early breeders.

The principles of scientific breeding were to be applied when choosing which cats to pair together. "Inbreeding increases the purity of a stock in so far as its genetical [sic] characteristics are concerned, and generally concentrates those of a recessive nature." He cautioned that the tendency to infertility or sterility was also concentrated and that excessive inbreeding resulted in extinction. He also discussed the importance of distant ancestors (up to 5 generations) where a rare trait or carried recessive was concerned and the importance of how closely the parents were related to each other. Much of this falls into the modern topic of 'inbreeding coefficients'. "Pedigree recording, correctly developed, represents a progeny test of the ancestors. In general, long pedigrees are of more interest to the historian than to the breeder-fancier. An animal in the fifth ancestral generation (great-great-great-grandparent) contributes only about 3.125 per cent of the inheritance of a kitten ; if this includes some particular and important trait, such as a desired coat colour which is rare in the breed, such a distant ancestor may become important. But for most purposes a thorough knowledge of three or four generations of the pedigree is all that the breeder really requires. It is more important to extend the knowledge than the pedigree." Among 21st century breeders, line-chasing has become a fascinating, and sometimes necessary, part of breeding in order to find out when or how a particular trait got into the breed.

Of the risks involved in repeated brother-sister matings, Jude wrote that such matings had been done experimentally in rabbits for 40 recorded generations, and in rats for over 150 generations. Many of those lines died out due to the fixing of undesirable characteristics, but the surviving lines became homozygous for an exceptionally large number of characters. In the cat fancy, close inbreeding (brother/sister, mother/son, rather/daughter) "should only be undertaken with cats for special purposes and in favourable conditions, and in building a strain or a new variety where close in-breeding becomes a necessity for a while, the breeder must have the time and ability to watch for the development of faults, and be prepared to suffer losses in some cases. An occasional mating of this nature in a strain is, however, unlikely to have any serious effects, whilst line-breeding - keeping to the same strain, but not mating such close relations - is usually desirable in the development in most forms of stock."

The term prepotency was a familiar and important one to breeders and usually meant that a particular sire stamped his progeny in his own image (since a single male could sire hundreds of offspring in his lifetime, while a female bore relatively in her lifetime, prepotency was thought to be a male attribute; females also had previously been considered as nothing more than vessels for the male's seed). Jude was able to explain why prepotency happened. It was usually a characteristic of inbred strains due to the prepotent animal having many dominant genes.

Inbreeding was, therefore, a useful tool if carefully managed and not excessive. Jude also defined and differentiated 'line-breeding' as a systematized form of inbreeding "The term is usually understood to mean building a pedigree in which one individual occurs repeatedly, but it is possible to line-breed to several individuals at once. It is not possible to line-breed without in-breeding to some extent, but it is possible to in-breed without line-breeding in this sense of the term, i.e., by mating brother to sister in every generation; some breeders, however, would call the latter line-breeding on the grounds that the animals mated belong to the same ‘bloodlines’. " The ‘bloodlines’ of any pedigree stock from racehorse to cattle to domestic dogs revealed the importance of line-breeding.

‘Outcrossing’ was defined as the introduction of an animal into a strain from another strain of like origin, or even from some isolated breeding in order to introduce desirable traits or reduce weaknesses. Continual outcrossing meant continually breeding together unrelated animals and the progeny owed as much to chance as to choice of mate. Pedigrees would become very involved (through the need to trace multiple lines) and almost useless to the fancier and, Jude wrote, an upsetting influence in any livestock fancy. The degree (of unrelatedness) and frequency of outcrossing had to be carefully managed to avoid introducing unwanted traits. "A point that the fancier should carefully guard against is allowing a fault to go too far before outcross is made. Obviously it must be easier to eliminate a weak fault rather than one which has become deep-seated, and it is found, too, that when an out-cross is made after long in-breeding, disastrous results may follow."

'Outbreeding’ meant a mating between two breeds, although many breeders used the term 'cross-breeding' or 'hybrid'. To further confuse matters, in the British cat fancy, for historical reasons a blue longhair was considered a different breed from the black longhair while in other cat fancies, the two colours were considered different varieties of the same breed. Jude defined cross-breeding as similar to out-breeding, but much more involved since the aim is to transfer a trait from one breed into another where it is missing or in decline or, perhaps, to create new breed. Once the trait was introduced, the cross-breeding must end. "Where a ‘new’ colour is introduced to a breed by cross-breeding, i.e., where the wanted colour is not already contained by the breed, the original breed is not of necessity altered. The introduction of red to Siamese to produce Red-Points is a case in mind. The Siamese breed is known through its distinctive marking. The introducing of red from another breed does not alter the distinctive breed marking. It still remains ‘Siamese’ and will breed true to that characteristic breed marking, i.e., the factors which do not allow full colour in the coat are unaltered."

In crosses between breeds of the same species, the resulting hybrids were generally larger in weight and skeletal dimensions due to hybrid or cross-bred vigour. This could be used to counteract excessive inbreeding. However, the added vigour tended to disappear in the following generations. "Whether the greater vigour is due to the unlikeness of two sets of genes brought together in fertilization, or to dissimilarity of egg and sperm constitution in other respects, is not yet fully investigated." Of inter-species hybrids, Jude gave the example of mules produced by mating the horse and the ass: "Hybrids of this nature are, in general, intermediate between the parents in size and conformation, but should the parents differ in a mutant character, the inheritance for that character is typically Mendelian. The present explanation of the failure of species hybrids to reproduce is that their chromosomes are incompatible. They are so diverse in constitution that they refuse to combine, and so their gametes, if produced at all, contain unbalanced assortments of genes, and are unable to survive." Perhaps he had simply overlooked the successful and fertile hybrids produced when domestic cats were mated to the Scottish Wildcat and to the African Wildcat, or perhaps he wished to discourage such hybrids.

One of the most discussed questions dealt with by Jude was whether or not peculiarities acquired by an animal during its lifetime could be passed on to the following generations. This had long been a viable theory and he wrote "Theories about all sorts of things in life are worked out, and are sometimes accepted as workable ideas, but with the march of time new theories are evolved which may be upsetting for the earlier ones, or even supersede them. Whether or not this may in any way apply in the case of heredity and acquired characters has still to be sorted out." He stated that according to the Mendelian theory of genetics, acquired characters could not be inherited because the germ cells were insulated from things that altered the animal's body during its lifetime. In the post-war era, one or two Russian scientists had formulated a new theory that oppose that of Mendelism. They maintained that since the germ-cells took part in the process of metabolism, the germ cells were not isolated and could be affected by changes in the rest of the body and in the environment. The environment could therefore make changes to the germ cells and the offspring would inherit qualities not derived from its own ancestors. "In the new theory it is not claimed that every acquired modification is inherited, but it is thought that certain physiological adaptations can sometimes be passed on. Mendelism regards only those inherited features which are already determined in the newly-fertilized egg as being ‘true’ heredity, any characteristic due, for example, to influences from the mother during pregnancy and lactation being regarded as ‘inborn’ but not inherited." Jude was referring to 'Lysenkoism' an anti-genetics theory based on Lamarckism that held sway in the Soviet Union between the mid 1930s and the mid 1960s. Genetics had been declared a 'bourgeois pseudoscience' in the Soviet Union in 1948 though by the mid 1960s, Lysenkoism was found to have caused mass starvation and serious, long-term harm to Soviet agriculture (in spite of this, Lysenkoism, continued to hold sway in communist China for many years after it was abandoned in the Soviet Union).

Scientific breeding and the building up of strains was restricted in practice because most cat breeders could only keep a small number of animals due to constraints of space and cost. Hence breeders needed to co-operate on agreed joint breeding plans. Such schemes had already worked well (and continue to do so into the 21st century). Jude's advice was to first concentrate on which traits should be retained or eliminated in the following order of importance: disease free, disease resistance, fertility and absence of deformities. Except in very special cases, those traits must come before the finer points of show features (conformation, colour, pattern) and during the first few generations breeders must be most ruthless in selection. Some 50 years on from Jude, many people question whether some breeders have lost sight of that order of importance and are deliberately breeding from unhealthy 'mutant' cats in their pursuit of novelty (some countries have even legislated on which mutations are unhealthy and not to be bred).

Accurate record-keeping was essential, detailing not only parentage, but also every modification produced, perhaps using a scoring method (with rare or important features receiving a higher scoring weight). No mating should be made without full knowledge of the cats' ancestry, especially for special traits. "Line-breeding is recommended - consistently to the best individual produced until a better one occurs, and then line-breeding to [the better individual]. The ‘blood’ of an outstanding animal can only be conserved by in-breeding to it whilst the animal is living, but close in-breeding should only be resorted to when an animal of very exceptional qualities, and with no outstanding faults, is available. Wide out-crosses should not be resorted to after a strain has been established, but some outside ‘blood’ may be introduced as may, at the time, seem necessary."

Jude summed up his treatise on scientific breeding thus: "For the intending fancier-breeder let us end this way. Make it your very definite first consideration that under no circumstances whatsoever will you be persuaded to purchase any animal without first being conclusively convinced that in the ancestry of that animal there is no trace of tendency to inherited disease or faulty reproduction. No matter how good-looking the animal may be, if you purchase one with such tendencies, you will be laying a foundation for building up for yourself endless disappointment and worry, and your hand will for ever be in your pocket. Good looks alone in livestock will carry you nowhere. Only healthy stock can allow success. A study of genetics does at least make these facts certain."


In 1971, the first edition of Roy Robinson's "Genetics for Cat Breeders" was published. With information drawn from breeders, scientific journals, research and private correspondence this became the gold standard of cat genetics books. It has become so much a part of cat breeding that after Robinson's death, the name was retained and the 4th edition (1999) was titled "Robinson's Genetics for Cat Breeders and Veterinarians" and had 5 co-authors. As well as current genetic information (colours, fur types, conformation and corrections to Jude's work) it details breeding methods and mathematical formulae for determining degrees of inbreeding. Genetic abnormalities are also described to aid the breeder in eliminating them from bloodlines. Breeders no longer described cats a "black" they were "black carrying blue" and many can give genetic formulae showing which genes the cat has based on knowledge of its pedigree.

In the fast moving 21st century, books are out of date almost as soon as they appear in print. The savvy breeder can turn to the internet for the latest developments - corrections, new mutations and software to record pedigrees and to predict the outcome of matings or to identify which genes a prospective mate should carry in order to achieve particular traits in the offspring. Where once anything beyond a 3 generation pedigree was of historical, rather than practical, knowledge, linechasing has become important for many breeders and some lines can be traced back almost a century (albeit with gaps and historical inaccuracies). The colours of ancestral cats can be retrospectively identified as "probably lilac" rather than "a pale blue strain" based on knowledge of their descendants.

The feline genome was mapped at the start of the 21st century. Genetic modification (GM) has been performed in laboratory rodents and there are hopes at producing non-allergenic GM cats. Genes from other species could be added to feline embryos, for example the gene for luminescence from a jellyfish. Cats have been cloned and, in theory, a neutered or infertile cat that goes on to become an outstanding prize-winner can now pass on its genes via cloning. Several mechanisms that can cause the elusive tortie male have been identified.

On the other hand, genetics has led to a schism between "genotype" breeders (the cats must be purebred for certain genes) and "phenotype" breeders (the cat must look the part even if it carries genes from an outcross). Better knowledge of genetics and strong selective breeding has led to "hyper-types" or "ultra-types" whose traits have been taken to such extremes that some no longer really look like cats. In response, some breeders have "traditional style" or "old style" versions of the breed in parallel to the showbench ultratype.

Legislators became involved in cat breeding in 1995 when they drafted the "European Convention for the Protection of Pet Animals". While ultra-typing continues unabated in America, there is European legislation against American-style "hypertypes". If enforced as law in the member states of the Council of Europe, ultra-typed Persians/Exotics (brachycephaly and brachygnathia), Manxes (spinal column defects), Bobtails (fused tail vertebrae), Scottish Folds (folded ears and skeletal defects), Sphynxes (hairlessness), Rexes (defective tactile hairs), Munchkins (a form of dwarfism) and their derivatives would all be banned as "abnormal" or "genetically defective". If the breeders do not amend their own breeding practices or where the characteristic could not be eliminated, the law would cause affected breeds to be "phased out". Blue-eyed white cats in any breed would also be affected due to issues of deafness and only bluee-eyed cats with certified good hearing could be bred. Polydactyl cats would also be banned under the misconception that the gene was semi-lethal (possibly confusing it with radial hypoplasia which can also cause a form of polydactyly).

Good knowledge of scientific breeding - genetics - would allow some of these traits to be eliminated and the ultra-type trend could certainly be reversed. Having come from a state of no genetic knowledge to one of good genetic knowledge, the future of scientific cat breeding may have as much to do with lawmakers and laboratory scientists as with selective breeding by cat fanciers.


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