196 



NORTH AMERICAN FAUNA 74 



Fig. 117. Examples of embryos and fetuses of Pacific walruses: (a) 0.4-mm free blasto- 

 cyst from a female taken on 14 May; (b) 6.1-mm elliptical blastocyst in the primitive 

 streak stage, early in nidation (25 May); (c) 7-mm newh- implanted neurula (arrow) in 

 the uterus (17 June); and (d) 61-mm fetus (20 July). (Photos by F. H. Fay) 



