514 



BERTRAM G. SMITH 



romeres are the transverse ridges on the inside rather than on 

 the outside of the brain. To a Hmited extent this view coincides 

 with that of Kupffer ('85 to '93), who maintained that the true 

 neuromeres are the transverse divisions of the open neural plate 

 rather than the later appearing structures in the neural folds. 



Most of the features of thi^ stage thus far described have been 

 observed in living as well as in preserved material. The liter- 

 ature on the early development of the central nervous system 

 has recently been reviewed by Griggs ('10) ; a more comprehensive 



177 



178 



179 



Figs. 177 to 179 Camera outlines of embryos of Cryptobranchus allegheniensis 

 in Stage 14, drawn from preserved material. X 5. 



Figs. 177 and 178 Posterior views showing late blastopore. 



Fig. 179 Lateral view showing position of the embryonic body at the close of 

 Stage 14. The egg is shown in its natural position with respect to the vertical 

 axis, which passes in the plane of the paper parallel to its lateral margins. The 

 embryo proper has a total length of about 155 degrees. This figure and figure 

 166 are drawn from the same egg. 



survey of the earlier work on the segmentation of the vertebrate 

 head is given by Locy ('95). Ishikawa ('08) has described seg- 

 mental divisions in the open neural plate of Cryptobranchus 

 japonicus. 



During this stage, if not already in the preceding stage, the 

 anterior or dorsal part of the blastopore becomes closed over, 

 while the ventral part persists as a transverse crescentic slit 

 (figs. 177 and 178). At the close of Stage 14 the embryo has 

 increased slightly in length (fig. 179); it now extends over about 

 155 degrees of the surface of the egg. This increase in length 



