The Nervous System of Amblystoma. 



443 





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Fig. 1. Surface views of the first four stages. A, B, C are views of entire 

 embryos and D, E, F are outline drawings of neural plates. These and the remain- 

 ing figures of this paper were drawn with the aid of the camera, a, anus; agd, 

 anterior germinal depression; bg, blastogroove; bp, blastopore; br, blastoporic 

 rim; id, infundibular depression; nee, neurenteric canal; pg, peripheral groove; 

 pgd, posterior germinal depression; teg, transverse cephalic groove. 



one showing no fusion. In Amblystoma the evidence for this 

 view is still stronger ; for when the posterior germinal depression 

 is formed the blastopore is still wide open, and furthermore 

 there is an appreciable distanc'e between the posterior end of the 

 depression and the anterior rim of the blastopore. It is not the 

 purpose of this paper to enter into a further discussion of the 

 morphology of the so-called the primitive groove. It is desired 

 merely to emphasize the fact that the groove which is here called 

 the posterior germinal depression arises independently of the 

 blastopore. 



