454 C. JUDSON HERRICK 



In Chrysemys marginata of 27 mm., cross sections show that 

 the medial and lateral nuclei of the septum are well differentiated 

 and there is a membranous sac or pocket which projects forward 

 on each side above the lamina terminalis and its commissures 

 (fig. 46). This is the recessus superior which Elliot Smith ('03) 

 has recognized in monotremes and other vertebrates and which 

 Mrs. Gage has recently demonstrated in a five weeks human em- 

 bryo (at the Boston meeting of the Association of American 

 Anatomists, Dec. 28, 1909). The paraphyseal tubules spring 

 from its dorsal surface and the lateral plexuses arise immediately 

 behind it. The recessus superior has been described in the gecko 

 embryo by Tandler and Cantor ('07). 



I have preparations of adult brains of Chrysemys marginata 

 by the Weigert method which show that here also there is an un- 

 differentiated region between the precommissural body and the 

 cortex hippocampi which contains fimbria fibers and scattered 

 small cells. This is a vestige of the unspecialized primordium 

 hippocampi which has not assumed cortical characters. In the 

 middle region of the septum the nucleus lateralis septi has grown 

 up dorsally into contact with the cortex hippocampi on its ven- 

 tricular side very much as shown for the alligator in fig. 66; but 

 both rostral and caudal to this level the primordium hippocampi 

 occupies the whole thickness of the wall, where it is bounded 

 below by the fissura limitans hippocampi. It is everywhere 

 separated from the cortex hippocampi by the fissura arcuata. 



In the adult box tortoise, Cistudo Carolina, the same conditions 

 prevail save that the lateral nucleus of the septum is smaller here. 

 Fig. 47 illustrates the relations immediately rostral to the inter- 

 ventricular foramen in Cistudo. 



In none of the turtles which I have examined, either embryonic 

 or adult, do any cells of the precommissural body extend back- 

 ward above the interventricular foramina, as in the frog and lizard. 



The relations of the telencephalon to the diencephalon are 

 clearly illustrated by figs. 48 and 49, where the resemblance to 

 urodele larvae is very striking. These sections of a 12.3 mm. 

 embryo of Chrysemys marginata are cut transversely to the sagit- 

 tal plane and so inclined that the dorsal surface is much farther 



