A EGG 



mtcropyle and micropylar cell 

 germinal disc 

 seam of operculum 



'i'^i* 



4 CELL 



D THIRD CLEAVAGE 



neural crest 



blastomeres 



biostodisc 

 embryo, 

 germinal ring 



blastopore 



E EARLY CLEAVAGE 



neural groove 



riM i lij i w . Wji i rx i entoden 

 notochord periderm 



G CROSS SECTION THROUGH EARLY EMBRYO 



nbryo 



somatopleure 



blastopore 



heart 



head 



otic capsule 



V' -,'- v^ ^pharyngeal openings 



somite— k.'.'.>'ic> 

 >(|.::v^ 



- segmental artery 



H 



:•'/////////// 



'///(A(A(ma/m '( 



LARVA AT HATCHING 



Figure 7-14. Stoges of Eptotretus A, shelled egg with anchor filaments ot either end; B, hp 

 of anchor filament enlarged; C, 4-cell stage; D, third cleavage furrows; E, early cleavage; F, egg 

 with biostodisc cop at animal pole; G, cross section through early embryo; H, blastoderm overgrow- 

 ing yolk mass; I, later stage with yolk enclosed by blastoderm; J, head of embryo rising off biosto- 

 disc; K, larvo at hatching. (After Dean) 



PLACENTA • 209 



