FOWL -TlfllM) DAY 



535 



I In- front end <f tin- bruin is n:\.-rseil in position, what was its 

 ventral side ha\ in-' conn- to In- dorsal. 



Tin- nirsodrriii sro'iiirnts have increased in number there heing 



am. 



v.c. 



U.O. 



a.e. 



FIG. 236. Third-day Fowl embryo (No. 47) viewed as a transparent object. 



a.e, edge of amnion ; am, amnion ; E, eye; //, heart; i.s, mesodfini se-nients; ot, otocyst ; 

 .--, indications of ] uootic mesoderm segments (?) ; /MI, vitelline aitcry : .<. visceral cleft II; *, portion 

 of planohnopleore buljiiuj; dmviiwauls into the yolk, forming a recess in wliidi lies the head of tlie 

 embryo. 



now al H>ut LI5-30 metotic segments and those towards the anterior 

 end are shewing a considerable amount of dorsiventral growth. 

 In some embryos (Fig. 236) the series of definitive mesoderm seg- 

 ments is continued far into the head region by what appear to 



