164 Journal of Comparative Neurology 



nosoma coronata (#^-'93). The epiphysis is a large vesicular 

 structure connected to the roof of the diencephalon by means 

 of an attenuated stalk which curves around cephalad over the 

 the supra-commissure. This peculiar curvature might lead one 

 to think that the epiphysis arises in front of the supra-commis- 

 sure but closer inspection reveals the origin immediately caudad 

 of it. 



The nerve in Sceloporus arising from the anterior part of 

 the supra-commissure could only be traced to the end of the 

 epiphysis which, coming to a point, reminds one of De Graaf's 

 statement that this proves that a vesicle has been constricted off 

 in the embryological development (p. 29). In Phrynosoma 

 coronata we were able to trace the nerve from its origin in the 

 supra-commissure to a point immediately below the parietal eye. 

 In Sceloporus the distance between the terminal points of the 

 bones of the skull between which the parietal eye is situated is 

 a great deal larger than that of Phrynosoma. Imbedded in the 

 subcutaneous tissue of the skull was found the parietal eye. To 

 this microscopic yet beautifully perfect structure reference will 

 be made below. The paraphysis of Sceloporus is an intricately 

 folded membrane. Two sac-like structures are found in it ; one 

 caudad of the hippocampal commissure forming the so-called 

 Zirbelpolster, the other cephalad of the hippocampal commissure 

 and extending out to the terminus of the epiphysis. Its walls lie 

 side by side, the caudal one being slightly corrugated. Thus 

 we find in Sceloporus a relation of the hippocampal com- 

 missure to the paraphysis which we think has heretofore re- 

 mained unnoticed. We would suggest as an explanation, that 

 in the ontogenetic development the fibres of the hippocampal 

 commissure passing over the thin membranous roof of the dien- 

 cephalon were developed before the folding of the paraphysis 

 so that when this did occur the roof was held down at this 

 point by the commissure and was pushed dorsad on either side. 

 The same anomalous relation was found and figured in Phry- 

 nosoma (Vol. Ill, Plate XII, Fig. 1). 



The Parietal Eye. Of all the degenerate organs in verte- 

 brates there is doubtless none that has aroused such general in- 



