518 C. JUDSON HERRICK 



EXPLANATION OF FIGURES 



26. Section from the same series as fig. 25, 75 micra faither caudad. 



27. Transverse section through the brain of a 29.6 mm. larva of Necturus macu- 

 latus. Drawn fiom a pieparation in the Harvard Embryological Collection (series 

 536, section 80). X 28. 



The right side is farther caudad than the left. The nucleus medianus septi 

 (s on the left) extends backward into the dorsal wall of the septum ependymal to 

 form a pars fimbrialis septi (p. f. s. on the right); cf. fig. 23. The fissura limitans 

 hippocampi (J. I.) separates the septum from the primordium hippocampi above. 



28. Section taken 28 micra caudad of fig. 27 through the septum ependymale 

 (s. epe?i.). The septum is interrupted by the interventricular foramen in the next 

 section caudad. (Haivard Embryological Collection, series 536, section 82). 



29. Transverse section through the brain of an old frog tadpole, approaching 

 the metamorphosis, taken in front of the lamina terminalis. Stained with haema- 

 toxylin and acid fuchsin. X 30. 



30. 31, 32. Three sections through the brain of another frog tadpole of the same 

 age as the last. Haematoxylinpieparations. X 30. 



30. Through the lamina terminalis immediately rostral to the interventricular 

 foramen. The nucleus medianus septi (precommissural body) is very large and 

 extends dorsally of the level of the foramen. 



31. Through the interventricular foramen. The small portion of the precom- 

 missural body above the foramen is the pars fimbrialis septi (Kappers). 



32. Through the anterior commissure. The section is somewhat oblique with 

 the left side farther caudad. On this side the rostral end of the nucleus of the hip- 

 pocampal commissure (n. c. h.) is shown. 



