506 C. JUDSON HERRICK 



EXPLANATION OF FIGURES 



1 to 5. A series of transverse sections through the brain of a specimen of Ambly - 

 stoma tigrinum 17 mm. long (about 35 days aftd fertilization). Method of Ramon 

 y Cajal. X 74. 



1. Through the olfactory bulb and illustrating the course of the nervus olfac- 

 torius and the division of the tractus olfactorius medialis into dorsal and ventral 

 portions. 



2. A short distance rostral to the intei ventricular foramen. The locus of the 

 fissura endorhinalis is indicated by an ependymal groove at/.e. The dorsal divi- 

 sion of the lateral olfactory tract (tr. olf. lat. dorsalis) characterizes the dorso- 

 lateral part of the hemisphere, tr. o. is a mixed system containing the medial and 

 lateral components of the basal forebrain bundle and the ventral divisions of the 

 medial and lateral olfactory tracts. 



3. Through the interventricular foramen near its rostral end. 



