26 A. S. PACKARD, JE., ON THE ANATOMY 



on the sides, not being lens-shaped as usual in the Myriopod and Arachnidan eyes, 

 as described by Graber and Grenacher. The cornea is laminated, as in the integument. 

 That the cornea is apparently normally concave in this genus, seems evident from 

 the fact that the soft parts next to be described fill the concavity of the cornea. The 

 solid parts, then, of this Myriopod, are quite unlike the larger corneal cones of Limulus ; 

 though in general, the corneal lens of the Myriopods examined by Graber appear 

 to be homologous with the cones of Limulus. 



When we compare the soft parts of the eye of Bothropolys and the Myriopods in 

 general with those of Limulus, we find nothing in common. 



In Bothropolys the soft parts consist of the layer of rather large, round, nucleated, 

 epithelial cells, situated next to the cornea, and called by Graber the " lens-epithelium 

 or vitreous-body cells," (Glaskorperzellen). This layer (absent in Limulus) is succeeded 

 by the layer of short, slender-pointed rods, as figured by Graber, with large nucleated 

 cells in the tissue enveloping them. This layer of rods, homologues of the rods of 

 other Tracheate and Crustacean eyes (also absent in Limulus) is succeeded by the 

 retina, a continuation of the hypodermal epithelial layer, the cells of the latter 

 being much more distinct and larger than the hypodermal cells of Limulus. 



The retina, whose structure differs from that of Limulus in having no " retinula," is 

 succeeded by the ganglion opticum, (absent in Limulus), which consists of a layer of 

 very large ganglion-cells rounded and overlapping each other ; their fibres leading away 

 from the eye, to form the optic nerve. 



Eye of Cermatia forceps. The eye of this Myriopod appears to be constructed on the 

 same plan as that of other myriopods though differing in some important respects. 

 Though Cermatia is said to have compound eyes in contradistinction from the ocelli of 

 other myriopods, the latter are truly aggregated or compound, the so-called " ocelli " being 

 made up of contiguous facets, the nerve fibres which supply them arising in the same 

 general manner from the optic nerves. 



The following description is made from sections made by Mr. N. N. Mason of Provi- 

 dence, and loaned me for description : — 



The eye is composed of a hemispherical, many facetted cornea, the lenses of which are 

 shallow, doubly convex, being quite regularly lenticular, the chitinous substance being 

 laminated as usual. 



Each corneal lens is underlaid by a retina about as thick as the cornea, the inner 

 surface of each retinal mass being convex. Corresponding to each lens is a-separate mass 

 of connective tissue, which increases in thickness from the end of the optic nerve 

 outwards towards the cornea, there being usually a clear interspace between each mass. 

 Within the broad stratum of connective tissue, next to the corneal lens within the retina, 

 is a layer of rounded "vitreous cells" or "or lens- epithelium" of Graber. This layer is 

 succeeded by the series of rather large visual rods, one in each mass corresponding to 

 each corneal lens ; these rods are long and sharp, conical at the end, the ends extending 

 one-half to two-thirds of the distance inwards to the inner edge of the retinal mass ; they 

 each possess a nucleus, and the connective tissue enveloping the rods is nucleated, while 

 there is an irregular layer of nucleated cells near or around the ends of the rods. 



