Fig. 18 Transverse section of an embryo of twelve somites to show the 

 amniotic position of the caudal anlages of the umbilical vein. Columbia Collec- 

 tion No. 547, slide 5, row 2, section 7, X 300. Reduced \. 



4 Funnol-like diverticulum of coelom 



1 Umbilical angiocyst 



2 Amnion 



3 Mesostroma 



between vessels of the splanchno- 

 pleure 



73 



