374 The American Naturalist. [May, 
processes of the cells belonging to this middle body, but which 
have not been impregnated. 
In other instances than those showing the fibers throughout 
their course nearly to the basement membrane of the retina, 
one finds fibers, or fiber Sroups, entering from each retinal 
element and continuing for some distance in through the pali- 
sade of fibers. 
In some cases cells belonging to the group just inside of the 
basement membrane, which were described by Berger as the 
cells of the granular layer, are found impregnated and with 
their processes connecting with the fibres just described. In 
other instances fibers with short lateral branchlets are to be 
noted, the branchlets occurring in the region of the outer fibril- 
lar body. 
From the details noted it appears that the elements from the | 
retina terminate each in a small tuft of fine branches in the 
outer fibrillar body, and come in contact with the fine lateral 
branchlets given off in the same region by fibers originating 
from the cells in Berger’s granular layer. These latter fibers, 
forming elements No. 1, then continue:on through the outer 
body, forming the palisade-like arrangement of fibers and the 
outer chiasma, and finally terminate arborescently in the 
outer lenticular mass of the middle body. The reasons that 
fibers from the retina seem to cross the outer body, forming a 
continuous passage between the basement membrane and the 
middle body is, it seems, that the lateral branchlets of elements 
No. 1 are very short, and the two small fibers are so closely 
applied together as to appear as one where they are heavily 
impregnated with bichromate of silver. 
From the elements forming the optic lobes of the higher 
erustucea, as described by Parker, these and the elements be- 
longing to the middle and the inner fibrillar bodies, noted in 
the figure as elements 2 and 3 respectively, differ in not form- 
ing a T-like figure, or in having a group of short lateral den- ' 
drites rather than one dendritic branch. This difference, it is 
plain, depends upon the location of the cell-body of the element. 
In the crustacea the latter, as shown by Parker, is situated 
between the fibrillar bodies that the two branches of its process 
