268 EFFA FUNK MUHSE. 



uniformly even thickness even to the ciliary process, a single 

 layer of cells continues on over the surface of the processes and 

 iris, but in Typlilops lumbricalis the retina at the back of the eye 

 is very thick and gradually becomes thinner till it ends a short 

 distance from the ciliary processes (Fig. 7). At this point the 

 arrangement could not be definitely determined in the sections. 

 At the back the retina, exclusive of the pigment layer, measures 

 .0725 mm. 



Ends of fibers were seen projecting inward from the ganglion 

 cell layer, but no definite fiber layer could be distinguished 

 (10 in Fig. 5). 



The ganglion cell layer (9 in the figures) consists of a single 

 row of large nucleated cells, somewhat irregularly arranged 

 (.008 mm.). 



The inner reticular layer (8) consists of a mass of fibers in- 

 terwoven in a close network. This layer measures, at the back 

 of the eye, .015 mm. 



The inner nuclear layer (6) consists of at least three layers of 

 cells, loosely arranged. The course of some of the fibers can be 

 followed among these cells. This layer measures .016 mm. 



The outer reticular layer (4) is very thin and consists of a few 

 fibers so arranged as to leave a great number of spaces between 

 the two nuclear layers. The distance between the nuclear layers 

 is about .005 mm. 



The sensory epithelium shows two distinct parts, an inner layer 

 of nuclei (3) and an outer row of cones (2). In the sections 

 these two were so separated that a loose tissue was visible, con- 

 sisting probably of the limiting membrane and ends of the Miil- 

 lerian fibers. The outer nuclear layer in the adult consists of a 

 single row of nuclei, with a mass of quite homogeneous material 

 about them. This part of the sensory epithelium measures .018 

 mm. The cones are pear-shaped bodies with the smaller end 

 pointing outward, and at intervals of every four or five a shorter 

 one occurs. Each element is differentiated into two parts. By 

 the iron haematoxylin process of staining, the outer small end is 

 densely stained, while the body of the element is a light granular 

 mass (Fig. 5). 



The pigment layer (i) is a continuous layer of even thickness, 

 similar in every respect to that of the garter snake. 



