PRIMITIVE SEGMENTATION OF THE VERTEBRATE BRAIN. “475 
Fic. 5.—Longitudinal horizontal section of Amblystoma punctatum, 
showing the olfactory region, the supposed olfactory neuromere, and the 
optic neuromere, with the relation to them respectively of the first nerve and 
the optic lumen with the cavity of the thalamocel (7. ¢.). 
Fie. 6.—Same at a lower level. 
Fic. 7.—Same at a lower level. 
Fie. 8.—Same at a lower level. 
The above series of the same specimen shows the gradual merging of the 
second neuromere into the optic diverticula (op. Zw.), and their immediate dorsal 
situation. The last also shows the first nerve in relation to the most anterior 
(neuromere ?) segment. 
Fic. 9.—Same, younger stage, shows the cavity of the epiphysis, the 
mesoceele (mw. c.), the fourth and fifth neuromeres, and fifth nerve. 
Fic. 10.—Same, shows same points as above, with part of sixth neuro- 
mere. 
Fie. 11.—Same, older stage, shows the sixth, seventh, and eighth neuro- 
meres ; and the fifth, seventh, and eighth nerves and auditory vesicles (az. v.). 
Fic. 12.—Same specimen at a low level, showing the sixth nerve ventral to 
the fifth. 
