I 16 OGY: [VoL. xe 
numerous and cannot be severally referred to in the present 
article. 
Whitman! has placed all the special sense organs in 
one group, expressing the conviction “that the segmental 
organs of annelids have formed the starting point for the 
development of the organs of special sense in the higher 
animals, not excepting even the eyes of vertebrates.” It 
is not, however, his suggestion of invertebrate relationships 
that I wish to bring out at the present moment, but the 
fact that he places the eye in a common group with the 
other sense organs. Contrary views are still held by many 
anatomists, and the whole question of the affinities of the 
vertebrate eye is in such shape, that any contribution which 
may throw light on the subject will be of interest to Morpholo- 
gists. It is for that reason that I have been led to offer, as 
a preliminary communication, some recently made observations 
of my own on the early development of the eyes, and other 
sensory organs, which arise in a similar manner, on the 
cephalic plate of elasmobranch embryos. 
I have shown in a previous number of this JourNAL? that 
certain steps in the early formation of elasmobranch embryos 
have escaped the attention of previous observers, and the first 
steps in the formation of the eye, also take place in the same 
stages of development that have been hitherto insufficiently 
studied. The elasmobranchs are especially favorable for 
studying the formation of the primary optic vesicles, but, 
strangely enough, their early history in these animals has 
been completely overlooked. 
Baltour®- ‘said, “Phe. eye does. not present in its) early 
development any very especial features of interest”? and this 
statement seems to have withdrawn attention from that organ 
in elasmobranch fishes. The Zieglers,t whose memoir on the 
1 Whitman, Some New Facts about the Hirudinea, Journ. Morph., Vol. 2, No. 3; 
April, 1889. 
2 Locy, The Formation of the Medullary Groove, and some other Features of 
Embryonic Development in the Elasmobranchs, /ourn. Morph., Vol. 8, No. 2, 
May, 1893. 
8 Balfour, Monograph on the Development of the Elasmobranch Fishes, p. 184. 
4 Ziegler, H. E. & F., Beitrage zur Entwicklungsgeschichte von Torpedo, Archiv 
fiir Mik. Anat., Ba. 39, Heft 1, January, 1892. 
