THE EYE OF PERIPATUS VF 
example, is continued over the eye without thickening. Below 
this, and between it and the lens, there are two cellular layers— 
an outer cornea and an inner cornea. ‘These correspond 
exactly to the corneal and subcorneal layers in Peripatus. 
The lens is non-cellular. 
We need not carry our comparisons further; they may be 
summed up as follows: (1) The retina of the Eye of Peripatus 
is of a simple and primitive type, and is found again in the ocelli 
of certain Diptera and in the eyes of some Myriapoda. It is 
also not unlike that of some Polychaeta. (2) The dioptrical 
parts of the Eye of Peripatus (lens and corneal layers) are well 
developed and, as pointed out by Lankester, are arranged 
in a manner quite unlike that met with in the Diptera, Myria- 
poda, or Crustacea. These parts, on the other hand, resemble 
very closely the similar structures of the Polychaete Vanadis. 
(3) The Eye of Peripatus possesses some features of a simple 
type met with in other Arthropod groups and in the Polychaeta, 
but so far as the Arthropoda are concerned it has followed its 
own line of evolution and remains quite distinct. 
LITERATURE CITED IN TEXT. 
1. Balfour, F. M.—‘‘ The Anatomy and Development of P. capensis”, 
“Quart. Journ. Micro. Sci.’, Vol. 23. 1883. 
2. Carriere, J.—‘ Die Sehorgane der Thiere’. Miinchen u. Leipzig. 1885. 
3. Hesse, R.—‘‘ Untersuch. ii. die Organe der Lichtempfindung: Poly- 
chaeta ”’, ‘ Zeit. f. wiss. Zoologie ’, Bd. 65. 1898-9. ‘ Arthropoda”’, 
loc. cit., Bd. 70. 1901. 
4. Sedgwick, A.—‘‘Monog. of the Development of Peripatus 
capensis ”, ‘Quart. Journ. Micro. Sci.’ 1885-8. 
5. Lankester, E. Ray.—‘‘ On the Structure and Classification of the 
Arthropoda ”, ‘ Quart. Journ. Micro. Sci.’, Vol. 47. 1904. 
6. ——- “ On the Structure and Classification of the Arachnida ’’, ‘ Quart. 
Journ. Micro. Sci.’, Vol. 48. 1904. 
