THE FATE OF HOMOZYGOUS YELLOW MICE 
131 
births or had eaten the young at the time of the preceding par- 
turition. An intensive study of such examples from both yel- 
low and white mice has failed to reveal any differences between 
Fig. 2 Abnormal blastula from the same set as the one shown in figure 1. 
This individual developed further than the one illustrated above, being larger, 
as well as more normal in form, and progressed further toward implantation. 
Phagocytes have overwhelmed one pole, and all the cells of the blastula are under- 
going cytolysis. X 240 
them. In both kinds the uterine lumen remains closed until 
the fifteenth day of gestation, although the destroyed epithelium 
is regenerated a day or two before this. No 'wandering' cells 
