MENDEL’S LAWS OF HEREDITY 399 
Guinea-pigs.—If a black guinea-pig of pure race be crossed with 
a white one the offspring will be all white, and if these are mated with 
each other the recessive white character reappears on the average in 
one in four of their offspring. These whites mated with each other 
produce only white offspring, while the black are as usual of two kinds, 
pure blacks and impure blacks. Similarly, as Professor Castle has 
shown, a rough coat is dominant over a smooth coat, and a short coat 
over a long coat. 
Rabbits.—Hurst paired white Angora rabbits (with pink eyes and 
silky hair) with “Belgian hare” rabbits (with pigmented skin, dark 
eyes, and short yellow fur). The hybrids were pigmented like the 
“Belgian hares,” but the fur was grey like that of the wild rabbit. 
These hybrids were inbred, and 14 distinct types resulted—an apparent 
“epidemic of variation” to which Mendel’s theory has supplied the 
clue, for four pairs of contrasted characters are involved in the hybrid 
inbreeding—namely, short hair versus long hair, pigmented coat versus 
albinos, grey versus black coat, uniform versus marked coat (Dutch 
marking latent in the albinos), and the 14 distinct types illustrate the 
possible combinations. 
As regards short hair versus long hair, Hurst found that when the 
short-coated hybrids were inbred they produced short-haired forms 
like the Belgian hare grandparent, and long-haired forms like the 
Angora grandparent. Out of 70 which reached the age of two months 
or more, 53 were short-haired and 17 long-haired—a close approxi- 
mation to the Mendelian anticipation, 52.5:17.5. Similarly, as 
regards pigmented coat versus albino, the hybrids, when inbred, 
yielded 132 pigmented and 39 albino forms—a close approximation to 
the Mendelian expectation, 129 : 43; and so on. 
Cats.—There are some interesting results as to colour (Doncaster). 
Thus, “pure’’ orange ? crossed by “pure” black ¢ gives tortoiseshell 
females and yellow males, but black crossed by orange gives black 
males or females, tortoiseshell females, and orange males. It seems 
that orange usually dominates over black in males, while in females 
the orange (for some unknown reason) is less dominant and tortoise- 
shell results. Male tortoiseshell cats are very rare. In this case the 
results are complicated by some peculiarity wrapped up with “sex.” 
When a male tortoiseshell is paired with a female tortoiseshell the 
kittens are tortoiseshell, orange, and black—which is what Mendelian 
theory would lead us to expect. 
Man.—Evidence of Mendelian phenomena in man is as yet very 
scanty. It appears that the condition known as brachydactylism, 
