The Nervous System of Amblystoma. 



457 



Fig. 5. Neuromeres in various stages of development. F is a diagram show- 

 ing all the features of the fully developed neural plate, a, anus; ad, anterior 

 depression; agd, anterior germinal depression; ap, anterior pit; bg, blastogroove; 

 id, infundibular depiession; li, lateral infolding; nl, n2, n3, n4, four neuromeres 

 of the procephalic lobes; nc, neural crest; pel, procephalic lobes; pen, postcephalic 

 neuromeres; pep, postcephalic plate; pg, peripheral groove; pgd, posterior ger- 

 minal depression; rs, retinal spot; teg, transverse cephalic groove. 



which is shown in fig. 4, C. The irregularity in the appearance 

 of the neuromeres suggests abnormality especially since the 

 cases are so very rare. It seems a fair conclusion that the varia- 

 tions mentioned in this paragraph in respect to size of neuromeres, 

 degree of development of right and left sides, and number of 

 neuromeres are only such as one might reasonably expect to 

 find in working over material of this nature. 



JOURNAL OF MORPHOLOGY, VOL 21, NO. 3. 



