THE FATE OF HOMOZYGOUS YELLOW MICE 



129 



TABLE 1 

 Sets of yellow-mouse embryos 



The destruction of abnormal blastulas by phagocytes (fig. 2) 

 is a very rapid process, similar to that described by Charlton ('17) 

 for unfertihzed mouse eggs, but in these cases probably a matter 

 of only a few hours, for it does not start until the embryos reach 

 the uterus, and by the time the normal ones are implanted, the 

 abnormal ones are represented merely by masses of phagocytes 

 and a few cell fragments. Whatever the exact nature of the in- 

 fluence that attracts the phagocytes, it is e\4dently active as 

 soon as the abnormal blastulas reach the uterus, for several 

 cases were observed where certain free blastulas were being 



