^-a^d 



:pf^P 



P^R 



^.^SM 



5 



fcq 



D 



Fig. 6. Neural plates of the seventh stage showing the downfolding of the 

 first neuromere and the development of neuromeres behind the procephalic 

 lobes, a, anus; agd, anterioi germinal depression; id, infundibular depression; 

 nl, n2, n3, n4, neuromeres of the procephalic lobes; pen, postcephalic neuro- 

 meres; pep, postcephalic plate. 



Fig. 7. Longitudinal sections cut a little to one side of the median line show- 

 ing development of neuromeres and infundibular depression, id, infundibular 

 depression; nl, n2, n3, n4, neuromeres of the procephalic lobes; np, neural plate; 

 pen, postcephalic neuromeres; pep, postcephalic plate; teg, transverse cephalic 

 groove. 



