56 COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 



In this experiment the parents both belonged to generation F. 2 , and 

 were respectively a dark-eyed animal which might be taken from any 

 of the classes (i) to (4), p. 48 and an albino which might be taken 

 from any of the three classes (7) to (9). We should, on the theory 

 of probabilities, expect half the eighteen pairs enumerated in Darbi- 

 shire's Table F as producing pigmented young to produce pink-eyed 

 offspring. Only three, as stated, gave this result, instead of the expected 

 nine. But the number of young produced by several of the pairs 

 was very small, being in four cases 3, and matings which should pro- 

 duce less than I in 4 of pink-eyed young (viz, 3 in 16) may well have 

 failed to produce any in litters of 4 or less. In the three matings cited 

 it is evident that both parents formed gametes bearing the pink-eyed 

 character, since pink-eyed young were produced. Accordingly the 

 dark-eyed parent must have belonged either to class (i) or to class (2), 

 and the albino parent either to class (7) or to class (9). In mating 

 K 10, the dark-eyed parent was probably of class (2), since no albino 

 young were produced, though the small number of young, three, leaves 

 this uncertain ; but in matings K 1 1 and K 15, it is clear that the dark- 

 eyed parent was of class (i), since albino young were produced in both 

 cases. There is nothing to indicate whether the albino parents in these 

 three matings were pure or hybrid as regards the pink-eyed character, 

 except the large proportion of pink-eyed young produced, which would 

 indicate that they were probably of class (9), i. e., pure. 



Accordingly, in Darbishire's experiments, we lack strong evidence 

 by breeding test of the occurrence of this class (9) only of all those in- 

 dicated on page 48. Yet I doubt not that the single albino born of pink- 

 eyed parents, as recorded in Darbishire's Table H, page 37, if tested 

 would prove to be of this sort, i. e., lacking entirely the dark-eyed 

 character, so that when mated with pink-eyed animals only pink-eyed 

 offspring would be produced. This result would be parallel with what 

 in mice Allen ( : 04) observed to be the relation of chocolate and choco- 

 late-yellow pigmentation to albinism, and what I, in guinea-pigs, have 

 shown to be the relation of red and of yellow pigmentation to albinism. 



HEREDITY OF ROUGH COAT. 



In certain varieties of the domesticated guinea-pig the hair has a very 

 peculiar arrangement, sloping away in all directions from certain points, 

 which are situated for the most part symmetrically along the sides of 

 the body, nearly coinciding with the centers of the typical pigment 

 patches. As a consequence the animal seems covered with cowlicks or 

 rosettes, between which the hair, sloping in opposite directions, forms a 

 series of ridges or crests. These are best seen in the so-called Abys- 

 sinian (the short-haired but rough) variety. (See PI. 2, figs. 3 and 4.) 



