492 'Journal of Comparative Neurology and Psychology. 



the neuropore is closed the front end of the neural tube presents a 

 prominent depression resting against the preoral entoderm and con- 



FiG. 28. Amblystoma p., a little more advanced thau the one shown in 

 Fig. 27. Parasagittal section through the optic ridge. X •^^• 



C.S. 



rpo. 



r.p. ch.op. 



Fig. 29. Amblystoma p., of about the same stage as that in Fig. 28. Model 

 of the right half of the brain seen from the medial surface, x 40. 



necting the optic vesicles (Fig. 25). This is the primitive optic 

 groove as described in Squalus. The model of this stage shows a 

 second angle at the front of the neural tube, separated from the 



