Sorensen, Study of Epiphysis and Roof of Diencephalon. 1 6 1 



tions of diverticles from the pre-paraphysis. The velum is seen 

 connecting the roof and base of the thalamus. 



Fig. 5, Plate XV, is a perpendicular section showing the 

 relations in the toad. The epiphysis is seen to be in communi- 

 cation with the roof and third ventricle. Its form is somewhat 

 different from that described in Menopoma. Its origin too, will 

 be seen to be immediately cephalad of the post-commissure, 

 with a long segment separating it from the supra-commissure 

 (See Osborn, p. 27). This position for the origin of the epi- 

 physis I believe to be peculiar to the toad. Arising thus cephalad 

 of the post-commissure the epiphysis runs forward to the supra- 

 commissure where it dips down. Numerous diverticles appear 

 from its wall throughout its length. We cannot agree with 

 Gotte (p. 16) who says that "the pineal comes to lie outside 

 the skull cavity in the toad." At least no such evidence is fur- 

 nished from our sections. We have found nothing to corres- 

 pond with his "vesicle and attenuated stalk." He himself quotes 

 Wyman, Ecker, Leydig, Rathke, and Gegenbaur as having 

 studied the epiphysis (pineal) in batrachians and that "they all 

 described the pineal as situated in the skull cavity, but confused 

 the vascular plexus of the third ventricle with the pineal, " which 

 to me seems hardly possible. 



Fig. 6, Plate XV, shows the conditions in the tadpole. 



Fig. 7, Plate XV, is a reproduction on a larger scale of a 

 drawing of the whole brain by C. L. Herrick (Plate XVII, 

 Vol. Ill, Jour. Comp. Neur.). With a few modifications in 

 form and size it would be seen to present the same struc- 

 tures as appear in the toad. The epiphysis with its 

 diverticles is larger and the plexus extends dorsad and cau- 

 dad over the supra-commissure and a portion of the epi- 

 physis. The structure arising immediately in front of the supra- 

 commissure and extending caudally over the epiphysis and post- 

 commissure which was marked nerve, in Professor Herrick's 

 drawing, upon closer examination appears to be connective tis- 

 sue. It will thus appear that no such structures as described 

 by De Graaf in Anura (p. 29), appear in the frog. The epi- 

 physis does not lie excranially nor have I found any trace of an 



