No. 566] 



SPOTTING IN MICE 



81 



Such animals would ordinarily form gametes AG, Ag, aG 

 and ag in equal numbers. These by independent recom- 

 bination would form 



But Hagedoorn gives figures which show that the pro- 

 portion which he obtains is nearer 2 agouti ; 1 black and 

 1 albino. This he supposes to be due to the fact that A 

 and G can never go into the same gamete. 



Now let us see what happens if this is the case. The 

 original heterozygotes will form only two kinds of gam- 

 etes instead of four, these will be aG and Ag. Now in the 

 recombination of these gametes the following result will 

 be obtained. 



So far, so good, but the trouble comes in testing the 

 albinos. Here I may quote from Hagedoorn, p. 126: 



• • • thirteen of these albinos have been tested by mating with black. 

 Without exception they have given black or equal numbers of black 

 and albino young. ... But never has one of those albinos produced 

 a single agouti young in a mating with black. Counting together the 

 colored young of such families I get 89 black young. 1 



This result is indeed remarkable, for on Eagedoorn's 

 own hypothesis the albinos should have produced in such 

 matings nothing but agouti young, " since they are all, 

 °y his hypothesis, homozygous for the agouti factor. 

 The evidence is incontestable; no repulsion of A and G 

 can have occurred. Has there been any coupling of these 

 two factors? If such was the case only gametes AG and 



