1 66 Journal of Comparative Neurology. 



stricted off forming a primary and a secondary optic vesicle. 

 There is a marked difference, too, between the nuclei of the 

 lens and those of the retina, the former being oval while the 

 latter are globular. A delicate blood sinus is shown to lie 

 within the capsule next to the retinal layer. 



Fig. 4, Plate XVI, is a drawing of the relations found and 

 explained by C. L. Herrick in Aspidonectes spinifer {Jour. 

 Comp. Near., Vol. I, p. 25). We have also studied the relations 

 in Cistudo and find them to be the same as in Aspidonectes. 

 They are however, considerably larger, the epiphysis having a 

 larger cavity and the plexus being more intricately plicated. 

 Fig. 5, Plate XVIII, shows the origin of the epiphysis in 

 Chelydra. The, entire roof is well described by Humphrey in 

 the July number of this Journal. Humphrey was not sure of a 

 communication between the cavity of the epiphysis and the 

 third ventricle. Our sections show such an opening. 



Thus far we have found the epiphysis to be either tubular 

 or vesicular. In snakes and mammals it assumes a third form 

 and is glandular. 



Fig. 1, Plate XVI, is a perpendicnlar section of the dien- 

 cephalic roof of an embryonic black snake (Bascanium con- 

 strictor). The glandular form and structure is clearly seen to 

 be connected by an attenuated stalk to the roof of the dien- 

 cephalon just caudad of the supra-commissure. The epiphysis 

 in this stage bends caudad instead of cephalad. What the re- 

 lation is in the adult we are unable to state. Cephalad of the 

 supra-commissure we find the much folded plexiform structure, 

 with this variation, however, that the sac-like structure forms 

 the cephalic portion of the paraphysis instead of the caudal as 

 is generally the case when only one sac is present. 



Fig. 2, Plate XVI, is a similar section of the garter snake 

 (Eutaenia sirtalis). The glandular epiphysis is in this case glob- 

 ular and is imbedded in connective tissue. The section is a little 

 torn but the relations are clearly defined. The same anomalous 

 condition is found in the paraphysis. The epiphysis does not lie 

 in as close proximity to the roof as in the black snake. Fig. 

 3, Plate XVI, is a transverse section of the epiphysis of the 



