The Nervous System of Amblystoma. 



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Fig. 3. Transverse sections of the open neural plate. E, F, G are highly magni- 

 fied to show the cell structure, agd, anterior germinal depression; bg, blasto- 

 groove; ng, neural groove; pgd, posterior germinal depression. 



3, B shows the posterior depression of the same embryo. The 

 difference between the two grooves is a difference of depth. 

 Fig. 3, C, a section of a slightly older embryo, shows the much 

 more sharply defined neural groove as it appears in the posterior 

 half of the neural plate. The walls of this groove form a more 

 acute angle than the walls of the posterior depression and the 

 depth of the groove is decidedly greater. The anterior end of 

 the blastogroove, shown in fig. 3, D, has about the same depth 

 as the neural grove but it will be noticed that the walls of the 

 blastogroove form a sharp angle with the surface of the neural 



