6o Journal of Comparative Neurology. 



the left ganglion habenula and likewise attached to the right 

 habena at two points. The inferior vesicle is at first, according 

 to both Studnicka and Kupffer, in connection with both the right 

 and left ganglia habenulae. The union with the right is soon 

 severed while that with ihe left remains. 



While the question of innervation needs further investiga- 

 tion, the early history of the vesicles would seemingly preclude 

 all possibility of their being considered as right and left mates. 

 Of course it is possible that each may represent one or several 

 pairs of fused sensory Anlagcn, but until some evidence is forth- 

 coming this is merest conjecture. 



In 1892 {Aiiat. Anz., Vol. VII, p. 217) the senior author 

 called attention to a remarkably early differentiation of the 

 bases of the optic vesicles in Amblystoma and Rana in the 

 following words: "I believe I have proved in Amblystoma 

 and Rana, that the lateral eyes are present as a pair of depres- 

 sions in the cephalic neurai plate." * * * " I hope to estab- 

 lish, beyond question, that they are present as distinctly differ- 

 entiated areas at the time the medullary groove first appears." 

 In a second paper {^Joiir. Morph. Vol. VIII, pp. 189-94) evi- 

 dence was adduced which seemed to demonstrate the validity of 

 the above statements. 



In 1893 Professor Locy gave notes upon the appearance of 

 like structures in the unclosed neural plate of Squalus acanthias. 

 In addition to these, other depressions were found which the 

 author called "accessory optic vesicles." The conclusions 

 drawn from these observations are here given in the words of 

 the author: "There are preserved on the cephalic plate of 

 Elasmobranchs (Squalus acanthias) at least two pairs of acces- 

 sory optic vesicles. 



These taken with the primary optic vesicles, give to the 

 embryo three pairs of rudimentary eyes." 



If these observations are correct, we have, as the author 

 states, "a multiple eyed condition in the embryos of these ani- 

 mals. This is common enough in the invertebrates, but has 

 not been previously noticed in Vertebrates." The rejuvenation 

 of an hypothesis which for a score of years has been continu- 



