294 Susanna Phelps Gage 



A reconsideration of the exact relation of parts seems de- 

 sirable. At its middle, the pallium extends over the cere- 

 brum (Fig. 97) and far around to the lateral aspect. Farther 

 cephalad it is divided by a mesal partition into two parts. 

 The cavities so enclosed are sometimes called lateral ventri- 

 cles. The partition extends caudad soon, however, ceasing 

 to form a complete separation but hanging as a plexus into 

 the common cavity of the prosencephal, the auliplexus. Cau- 

 dad the pallium opens into the dorsal sac, paraphysis (Fig. 

 98). At the level of this figure it is seen to be reflected 

 laterad over a rounded ridge which, in tracing caudad, is seen 

 to be directly ventrad of the knob known as the habena (Fig. 

 99). The little sulcus si is the caudal extension of the lateral 

 pocket formed by the pallium (Fig. 98 si), and the outer border 

 of this pocket z, corresponds to the union of pallium and cere- 

 brum (Fig. 97 z). 



In the lamprey a section (Fig. 106) which cuts the habense 

 as does figure 99 in amia, shows that ventrad of the habena 

 on the left is a sulcus, on the right a membranous exten- 

 sion of endynia. Following these cephalad (Fig. 105) the 

 supporting columns of the habenae disappear and the lateral 

 pockets of endyma extend beyond the cerebrum, while be- 

 tween them arises the small sac here called the paraphysis. 

 At the side these sacs are reflected over the lip of the cere- 

 brum. Imagine the dorsal limb of the cerebrum (Fig. 105) 

 revolved laterad and then in their essential relations these 

 sacs are an exact counterpart of the pallium of fishes, though 

 the great cephalic extension of the left habena disguises the 

 fact somewhat. 



In amphibia and higher forms is it possible to recognize 

 such a membrane? In figure 22 are seen sulci ventrad of the 

 habense. These traced cephalad become the slight lateral 

 recesses seen at each side of the opening into the paraphysis 

 (Fig. 21, 53, 20, pi.). In figure ig the membrane is divided by 

 the intrusion of the auliplexus. Cephalad of the opening of 

 the port^ the union of the membrane with the cerebrum is 

 characterized by a reflection of endyma over a rounded ridge 

 (Fig. 18, loi z), at the ventral end of the mesal wall of the 



