242 Journal of Comparative Neurology and Psychology. 



which he sets forth does not deal with the same field as that 

 which I have dealt. The two hypotheses may prove to be con- 

 sistent. At one point, however, they are absolutely opposed. 

 BovERi bases his reasoning on the assumption that the eye, 

 both in Amphioxus and in vertebrates, is a ventral structure. 

 I have supposed, for reasons stated, that the vertebrate eye is a 

 dorsal structure. If the eye of Amphioxus is necessarily to be 

 regarded as a ventral structure, I doubt whether there is any 

 relation between the eye of Amphioxus and that of vertebrates. 



Morphology of the lens. 



At this time when the lens is being made the subject of 

 experimental investigation it would not be profitable to discuss 

 whether it belongs to the series of epibranchial placodes, or to 

 the dorso-lataral series, or is a structure of an entirely different 

 character. Kupffer's hypothesis that it is a modified epi- 

 branchial placode fits very well with the absence of the gill slit 

 and the visceral rami to which such a placode would belong. 

 On the other hand, the invagination of the lens suggests relation 

 to the lateral line organs and the auditory vesicle. This is 

 strengthened by the fact noted above that in Gymnophiona the 

 placode of the supraorbital lateral line nerve forms first as 

 a vesicle like the auditory vesicle. 



Morphology of the pineal organs. 



In spite of the great number of investigations bearing upon 

 these organs they still remain only imperfectly understood, 

 owing probably to their very rudimentary character. In ad- 

 dition to their general structure whicli fits them to be light per- 

 cipient organs, two facts point to a relation between these and 

 the lateral eyes. These facts are the presence of rods or cones 

 in Petromyzon (116) and the presence in the lateral walls of the 

 diencephalic and mesencephalic neuromeres of pouches similar 

 to the optic vesicles which may develop into the epiphyses (84, 

 125). If the epiphyses are formed from lateral pouches of the 

 brain wall, as seems probable, it is not known whether a pair 

 of such pouches fuse to form a median organ, or one of the 



