Sorensen, Study of Epiphysis and Roof of Diencephalon 157 



In another number he gives a perpendicular section through 

 the brain of a larva of Petromyzon fluviatilis, 4. 2 cm. long, 

 which is also reproduced. 



ca, coramissura anterior ; cb, Kleinhirn ; cp, commissura posterior ; cs, com- 

 missura superior ; D, Shaltstiick ; Md, Mittelhirndach ; Mg, Grenze der Mittel; 

 hirnbasis; O, Opticus; P, Paraphyse ; Pb, Rautenhirnbasis ; Pn, Recessus 

 Neuroporicus (Lobus olfactorius impar); Zb, Zirbelblaschen ; Zp, Zirbelpolster 

 Zs, Zirbelstiel ; z, Ahlborn's " unteres Zirbelblsachen." 



Personal Investigation. 



In the following work the object has been to make a com- 

 parative study of the epiphysis and roof of the diencephalon 

 in as many types as have been at our disposal. We are not 

 sure that the ground covered has been sufficiently exhaustive to 

 draw many conclusions, yet we have been struck by the great 

 similarity between the relations found throughout the different 

 groups from the fishes to the mammals. Among the fishes the 

 following have been studied : Ictalurus lacustris, Lophius pisca- 

 torius (Fishing frog), Lucioperca, Trutta fario, Hyodon, Cy- 

 cleptus elongatus, Scaphirhynchus platyrhynchus, Lepidosteus, 

 Blicca, Belone. 



The epiphysis of Ictalurus lacustris has been studied and 

 described by C. L. and C. Judson Herrick {jib- 91) and by C. 

 Judson Herrick 1 but without drawings showing the exact rela- 

 tions of the various parts. For this purpose we have made 

 drawings from two different series available (Plate XIV, Figs. 

 2-4). Fig. 2 is a perpendicular section showing the origin of 

 the epiphysis immediately caudad of the supra-commissure. It 



Kansas Academy of Science, '9i-'92 p. 71. 



