46 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 
(pr) are transverse sections of the distal prisms of the prism cells, 
the less numerous and lighter areas (pyr) are transverse sections 
of the pyramids of the pyramid cells, and the large oval heavily 
pigmented areas (Ip) are the transverse sections of the long pigment 
cells. The dots within the two first named areas represent fine fibers 
in the axes of the prism and pyramid cells, to be described below. 
The presence of three kinds of cells can again be readily seen in 
such Figs. as 4 and 7, in which the elements of the retina are cut 
parallel to their long axis. (Fig. 22.) Again, a transverse section 
through the most distal part of the pigmented zone of a slightly 
pigmented retina (Fig. 2) also shows us the presence of three kinds 
of elements. The larger and more heavily pigmented areas (lp) are 
the long pigment cells; the smaller, lighter areas (pyrc) with a 
central dot are the pyramid cells, and the more numerous dots, with 
no definite polygonal areas outlined about them (prc), belong to the 
prism cells. Thus, I believe, we have conclusive evidence of the 
existence of three kinds of cells in the retina of the distal complex 
eye: 
(a) The prism cells are the more numerous, and, as the name 
implies, end distally in a vitreous polygonal prism (Figs. 4, 7, 22, pr). 
The prismatic structure of the vitreous body is also shown in Figs. 
10 and 11, which are drawn from a macerated preparation of Conant’s. 
(See the descriptions of these figures.) 
In Figs. 4 and 7 the prism cells correspond to the cells with 
the darker nuclei (npr); in Fig. 2 they are represented by the dots 
without defined polygonal areas about them (pre), and in Fig. 1 by 
the most numerous areas (pr). These cells, then, consist of a centrad 
portion with nucleus, a pigmented portion with granules of a dark- 
brown pigment, distal from the nucleus, and a distal vitreous prism 
which extends to the capsule of the lens. 
In the axis of each prism is a fine darkly-staining fibril extending 
the entire length of the prism. I found no good evidence that this 
fiber extends into the capsule. Centrad this fiber is continued 
through the pigmented part of its cell and approaches to or near 
the nucleus (Fig. 2, dots without defined polygonal areas; Fig. 7, 
part of retina left unpigmented). In some instances I could trace 
this fiber quite to the nucleus, while in others it ended before reaching 
the nucleus or a little to one side of it. I am inclined to believe, 
however, that it extends past the nucleus and is continued as a nerve 
