Sorensen, Study of Epiphysis and Roof of Dicnceplialon. 159 



(Plate XIII, Figs. 1 to 4) have been fully described by C. L. 

 Herrick (jic—'gi) and are here reproduced merely for the sake 

 of comparison. 



Two other fishes have been studied, namely Blicca and Be- 

 lone. In Blicca (Figs. 9, Plate XIV) a horizontal section shows 

 the origin of the tubular epiphysis caudad of the supra-commis- 

 sure and also shows the plexus lying in front of the supra-com- 

 missure and presenting the appearance of a sac. In Belone 

 (Figs. 5-6, Plate XIV) we find structures similar if not identical 

 with those already described in the catfish. A vesicle formed 

 from the epiphysial tube lies upon the thin plexiform roof of 

 the third ventricle. 



To sum up, then, the conditions which are found in fishes 

 we can say that in general they are the simplest found in any 

 of the groups. The epiphysis is usually a long, slender, tube, 

 arising from the roof of the third ventricle immediately caudad 

 of the supra-commissure. It is sometimes straight and some- 

 times curved, and extends cephalad over the roof of the dien. 

 cephalon and over the pallium. In the trout and Lepidosteus 

 numerous diverticles arise from the walls, while in a small catfish 

 and in Belone a vesicle composed of a single layer of cells is 

 formed at its cephalic extremity. In the eel which is remark- 

 able in many respects we believe that the epiphysis is a gland- 

 ular structure imbedded in an enormous mass of plexus. The 

 sections however were oblique and imperfect and as the exact 

 relations were not traceable no drawings were made. 



The plexus in fishes is generally very simple in some cases 

 being merely the thin roof of the third ventricle while in others 

 as Lepidosteus it is intricately folded and vascular. 



The amphibian brain presents many modifications in the 

 structures forming the roof of the diencephalon. 



Material. Menopoma allegheniense, Amblystoma puncta- 

 tum, Salamander (species unknown), Bufo lentiginosus, Hyla 

 versicolor, Rana halecina (Leopard frog.) 



The structures present in Menopoma (Figs. 1-2, Plate XV) 

 show a relatively far greater development of the paraphysis 

 (plexus) than is found in fishes. The epiphysis as shown in a 



