98 Journal of Comparative Neurology 



Whether this is true in the adult I am not able to say with con- 

 fidence, though the evidence is in favor of it. Herrick (44) says 

 that the cavities do communicate in turtles but his observations, 

 I believe, are based upon the brain of Cistudo. In the adult 

 the epiphysis is relatively longer than in the embryo but the 

 width has not correspondingly increased. The enlarged distal 

 portion has become lobulated by the pressure of the surround- 

 ing tissues. It is easily differentiated from the surrounding 

 plexus, and careful study fails to reveal any bipartite structure 

 or communication of its cavity with the cavity of the underly- 

 ing structures. 



That portion of the roof of the diaccele lying cephalad of 

 the supracommissure is still a subject of dispute, both as to the 

 number and character of its outgrowths and as to its cephalic 

 limit. The most generally accepted interpretation is, that in 

 this region two outgrowths are to be found, the most cephalic 

 and earliest developed of which originates as an outgrowth of 

 the prosencephal, while the other is formed from the growth of 

 the diencephalic roof. The existence of two outgrowths in this 

 region was first shown by Francotte (26) and to the cephalic 

 one Selenka (74) applied the term paraphysis. Hoffman (49) 

 figures and describes but one outgrowth which he says originates 

 "between the prosencephal and diencephal." Kupffer (52) in 

 Acipeiiscr embryo figures two outgrowths separated by a wide 

 velum transversum. He considers the velum to be the bound- 

 ary between the brain segments. Herrick agrees with this view. 

 Mrs. Gage shows the presence of two outgrowths in Diemyc- 

 tylus, the cephalic of which she believes to mark the boundary 

 between the brain segments. According to her view the velum 

 belongs to the diencephal, and from the velum is developed the 

 diaplexus which reaches, in the amphibian brain, an enormous 

 development. Edinger (22) figures an ideal sagittal section of 

 the reptile brain with a velum extending cephalad, forming the 

 plexus of the prosencephal. The other parts have the usual 

 relations. Sorensen (76) shows two evaginations in the duck 

 embryo separated by the velum. To these he applies the terms 

 pre- and post-paraphysis, following the nomenclature of Herrick. 



