864 The Arthropod Eye. -  [October, 
ophore are slightly enlarged. It is, however, with regard to the 
pedicel that one of Dr. Patten’s most important discoveries were 
made. According to Grenacher, this part (his rhabdom) is 
secreted by the surrounding pigment cells, but Dr. Patten claims 
that it is in reality but the coalesced proximal ends of the four 
retinophore. 
Surrounding the portions of the eye already described are a 
varying number of pigment cells (about sixteen in Crangon); 
around the nucleus these are large, but at either extremity they 
thin out into fine threads or rods which, according to Dr. Patten, 
_ extend, like the retinophorz, from the epidermis to the basal 
' membrane. I have not been able to trace these extensions except 
: in part, and hence have omitted them in the drawing. It seems | 
probable that a variation occurs in these rods with the species, f 
_ though Dr, Patten (p. 637) is inclined to the contrary view. | 
At the base of the ommatidium a large nerve fiber (æ) is seen 
coming from the deeper portion to the base of the pedicel. Ac- 
cording to Patten this divides just before reaching the basal mem- — q 
brane, and gives off branches to each of the cells (pigment cells, 
retinophorz) composing the optic element. And farther, branches 
go to adjacent elements so that each ommatidium receives Its | 
“nerve supply from four different main bundles. The arrangement 
of these is very complex, and need not be described. The fiber, a 
however, which penetrates the axis of the pedicel seems of more 1 
importance to a conception of the phenomenon of vision, and l 
-hence a word is necessary. It runs through the pedicel and é 
© Style and penetrates the crystalline cone, where it gives off fine 
_ fibrillae which radiate in every direction towards the outer wall. 
_ These are points which seem to have escaped all previous a 
servers, The writer has traced the axial fiber into the cone, bu 
Tas not seen the other details. 
Of the various theories and conclusions advanced by Mr. ra 
ten as results of his studies, we have room to mention but three - 
First, the existence of the radiating fibers in the crystalline con® 
t 
ua e compensation for lack of adjustment, for no "a 
e the image produced by the lens may fall, it will fall 1 
