86 Experimental Zoology 



recessives and of extracted dominants cannot be accounted for, 

 if they are supposed to have been formed by the union of pure 

 germ-cells. On the contrary, he thinks that the results become 

 intelligible only when the ancestry of these forms is taken into 

 consideration. In other words, if "pure" recessives and "pure" 

 dominants are really pure (as modern Mendelians have as- 

 sumed), the ancestry of such forms could be ignored ; but since 

 the results are inexplicable on this assumption, the most rea- 

 sonable conclusion is that the germ-cells are not pure. So far 

 I am in agreement with Darbishire; but if this conclusion is 

 meant to imply that the Galtonian assumption in regard to 

 inheritance in these cases is the only alternative, I should dis- 

 sent. I have tried to show how the Mendelian results may 

 still apply without assuming that the gametes are pure, but by 

 assuming that they show alternate dominance and latency. 



Darbishire also crossed some of his first hybrids (F^ with 

 albinos and obtained 368 albinos and 378 dark-eyed piebald 

 (or sometimes uniformly colored) mice. This gives a close ap- 

 proximation to the Mendelian expectation. He found, more- 

 over, in this generation that the gap between the albinos and the 

 least- colored individuals was greater than among the offspring 

 of hybrids (FJ when inbred. It is also interesting to note that 

 with this cross the pigmented eyes appeared in all the piebald 

 offspring. In other words, the latent color, eye-pigment, is 

 maintained in the cross, since it dominates the pink-eyed type. 

 Darbishire notes especially that these offspring (obtained from 

 the hybrid and the albino) have more white in their immediate 

 ancestry than have the offspring of the hybrids when inbred ; yet 

 the offspring show actually less white, and show more often the 

 wild color and black (as compared with yellow and fawn color). 

 The meaning of this he finds obscure, but possibly the results 

 may be accounted for on the assumption of the latency of pig- 

 ment in one or both parent types, which is brought out by 

 crossing. 



The subsequent history of the three classes of individuals ob- 

 tained by inbreeding the first hybrids (F^ is as follows : (i) The 



