3G8 JOHN WARREN 



eye probablj^ crosses from one side to the other as observed by 

 Dendy and de Klinckowstrom goes to prove that the pineal out- 

 growths are really bilateral. My specimens of Lacerta and 

 Chrysemys did not show this bilateral arrangement. The region 

 of the pineal organs is very thoroughly considered by Gaupp 

 (34), and Studnicka (95) in Oppel's Lehrbuch, V, 1904. 



SUMMARY AND CONCLUSIONS 



1. After the appearance of the primary fore brain vesicle the 

 prosencephalon is subdivided into telencephalon and diencephalon. 

 The diencephalon undergoes a further subdivision into two seg- 

 ments, the cephalic one being the parencephalon and the caudal 

 one the synencephalon or pars intercalaris. There are, there- 

 fore, three subdivisions to the fore brain. 



2. The first segment or subdivision is the telencephalon, which 

 is bounded caudad by the velum and the ridge passing from 

 the velum to the optic commissure. From its roof develop the 

 paraphysal arch, paraphysis and telencephalic choroid plexuses. 

 From its lateral walls arise the hemispheres and ventrad to them 

 the optic vesicles. In the floor is the optic recess and opening of 

 the optic stalk. 



3. The • second subdivision is the parencephalon, which is 

 bounded caudad by the hinder wall of the epiphysis dorsally, and 

 by the tuberculum posterius ventrally. Between these points 

 there is a slight ridge in early stages. From the roof arise the 

 post velar arch, diencephalic plexus, epiphysal arch, both pineal 

 organs, epiphysis and pineal eye, and the supra commissure. In 

 the floor are the infundibular and mammillary regions. 



4. The second subdivision of the diencephalon is the synen- 

 cephalon, or pars intercalaris. It is bounded caudad by a dorsal 

 groove and a ridge which ends below at the highest part of the 

 habenular flexure. Its floor is limited and the segment is often 

 wedge shaped. In the roof a portion of the posterior commissure 

 develops. 



5. The mid brain probably is subdivided into two segments 

 after the primary mid brain vesicle is formed. 



