48 COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. 



From this it is clear that the five albino parents which gave the result 

 just described transmitted in approximately half their gametes the 

 pink-eyed and in half the dark-eyed condition. These albinos are com- 

 parable in the matter of the pink-eyed character with my albino guinea- 

 pigs of Table E in the matter of black coat-pigment. A close parallel 

 exists throughout the two cases. Darbishire's original albinos all con- 

 tained latent the character pigmented eye. This character was invaria- 

 bly brought into activity by across with the centripetally pigmented but 

 pink-eyed race. That race would seem not to have possessed the 

 character eye-pigmentation, even in a state of latency which a cross 

 with albinos would bring into activity ; for half the gametes formed 

 by the hybrids apparently lacked the character eye-pigmentation, and 

 that character was as often associated latent with the albino character, 

 as it was associated active with the alternative character, standing for 

 centripetal pigmentation. If so, the hybrids must have formed with 

 equal frequency gametes of these four sorts: (i) pigmented coat, 

 pink-eye,* (2) pigmented coat, dark-eye, (3) albinism [pigmented coat 

 and pink-eye latent], (4) albinism [pigmented coat and dark-eye latent]. 



Hybrids forming sets of gametes like these, when mated inter se, 

 should produce young visibly of three classes in the proportions, 9 

 dark-eyed pigmented to 3 pink-eyed pigmented to 4 albino. The num- 

 bers observed by Darbishire are 287 (or 284?) dark-eyed pigmented, 

 131 (or 134?) pink-eyed pigmented, and 137 albino young. 



On the hypothesis which I have suggested, these young, though 

 visibly of only three different sorts, should really fall into nine classes, 

 whose numerical proportions are theoretically as follows :f 



Class (5). 2 P p (A p)\_ 3 pigmented 



Class (i), A,Pd (A p) 1 Cla&s (6), i Pp ) pink-eyed. 



Class (2) , 2 P d (p) I 9 pigmented 



Class (3\ 2 P d(A d} \ dark-eyed. Class (7), 2 A {dp] ) 

 Class (4), i Pd J Class (8), i A [_d d~\ [^albinos. 



Class (9), i - 



This classification rests on the assumption that eye-pigmentation may 

 be inherited apart from coat-pigmentation, i. e., that the primary 

 hybrids are really dV-hybrids in the Mendelian sense. It involves the 

 further hypothesis that eye-pigmentation was invariably latent in the 

 original albino stock used, and as invariably absent from the pink-eyed 



* Although the pink eye is due merely to absence of pigment from the eye, 

 just as albinism to absence of pigment from the eye and coat, it is convenient 

 in both cases to speak of the negative character as if it were positive. This can 

 be done, I trust, without confusion to the reader. 



t EXPLANATION. A = albino; P = pigmented; d dark-eyed; / = pink- 

 eyed; ( ) indicate recessive characters, [ ] latent characters. The relative 

 frequency of occurrence of individuals of each class is indicated by a coefficient. 



