PLATE 4 



EXPLANATION OF FIGURES 



(Cryptobranchus allegheniensis) 



All the figures are from preserved material fixed in bichromate-acetic-forma- 

 lin. X 4. 



216 Stage 7.5. Equatorial view. 



217 Stage 8.0. Upper hemisphere. 



218 Stage 9.5. Equatorial view. 



219 Stage 10.5. Equatorial view of an embryo nearly ready for gastrulation. 



220 Stage 11.4. Early gastrula, showing the dorsal lip of the blastopore. 



221 Stage 11.5. Antero-dorsal view of a gastrula, showing the fenestra. 



222 Stage 11.6. Anterior view of a gastrula, showing the fenestra. 



223 Stage 12.4. Dorsal view showing early neural plate and neural groove. 



224 Stage 12.4. Posterior view of the same embryo as in the preceding 

 figure, showing the yolk plug and a part of the neural plate and neural groove. 



225 Stage 12.5. Dorsal view showing the neural groove and the dorsal lip 

 of the blastopore. Figure 143 is drawn from the same embryo. 



226 Stage 13.4. Dorsal view showing early neural folds. 



227 Stage 13.5. Posterior view showing the form of the late blastopore, and 

 the i)osterior part of the neural plate. 



566 



