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 (Ip) are 

 the long pigment cells; the smaller, lighter areas (pyre) with a 

 central dot are the pyramid cells, and the more numerous dots, with 

 no definite polygonal areas outlined about them (pro), 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 (pro), 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 



