COAT CHARACTERS IN GUINEA-PIGS AND RABBITS. lj 



to interpret the phenomena on some such hypothesis as that of Galton. 

 He states the matter very clearly (p. 24) as follows : 



It is well known that according to this [MendelianJ view the hybrid contains 

 equal numbers of germ-cells which produce the dominant character, and of those 

 which produce the recessive; and this is said to be true of the hybrids however 

 far the individual is removed from the original cross, whether it is the result of 

 the cross (i. e , the hybrid) or the great-great-grandchild of this. This is the 

 ground on which the doctrine of the purity of the germ-cells and the law of 

 ancestral heredity flatly contradict one another; the former asserting that DR x 

 DR will produce 25 per cent DD, 50 per cent DR, and 25 per cent RR for a 

 very great if not an indefinite number of generations ; the latter maintaining that 

 the further the individual hybrid under consideration happens to be removed from 

 the cross the less albinos will it produce ; and that two hybrids whose mothers were 

 albinos will produce more albinos than would two hybrids \vb--> have no albinos 

 in their pedigree later than their great-great-great-grandmother. This seems to 

 me to afford a case in which experiment could provide a decisive answer. 



In this statement I heartily concur. 



The experiment which Darbishire made was this. He made three 

 different kinds of matings between animals which, we are told, were 

 hybrids, (i) In one case each of the two animals mated had one albino 

 and one pigmented parent. (2) In the second case, one animal was of 

 the parentage just described, the other was born of two pigmented par- 

 ents. (3) In the third case, the parents of both animals were pig- 

 mented. In brief, there were tivo albino grandparents in case (i), one 

 albino grandparent in case (2), and no albino grandparents in case (3). 

 The ancestry back of the grandparents was the same in all three cases. 

 The conditions are thus very simple and should, as Darbishire suggests, 

 give a decisive test. Darbishire states that 



This is a seemingly conclusive demonstration of the correctness of 

 Darbishire's contention ; but in fact Darbishire's results, when carefully 

 analyzed, prove just the opposite of his deduction. 



Fortunately he has recorded in an appendix the various litters from 

 which the totals given are made up. An examination of these records 

 makes it evident that his so-called "hybrids" were not all hybrids. 

 In mating (i) the animals used undoubtedly were hybrids, since each 

 had, as stated, one albino and one pigmented parent. It is noteworthy 

 that in that case the Mendelian expectation of 25 per cent albinos is 



