880 DEVELOPMENT AND STRUCTURE OF PINEAL EYE IN LACERTILIA, 



nucleus, and a portion of the cell suVjstance that has taken the 

 stain to the same degree. These cells likewise haA'e processes 

 which proceed up and down. 



Fourth Layer. — (a). A layer of cells (xV") similar to the second 

 layer (iV). (b). Two layers of triangular-shaped elements with 

 processe.s springing from the angles, and running in all directions. 

 These bodies take the stain quite as deeply as the spindle-shaped 

 ones above, and so no nucleus could be detected. 



Fifth Layer — (a). A layer (>.V') of spherical cells similar to the 

 second and fourth layers, (b). A layer (y") of spindle-shaped 

 bodies similar to, though more elongated than, the third layer. 

 The processes from this layer run up sometimes to the rods 

 themselves, but particularly do the processes run down to the layer 

 of connective tissue below. As in the third layer these bodies 

 stain very deeply. 



Sixth Layer. — A clear region (C.A.) which is more noticeable 

 in more advanced stages. It has no cellular elements in it, and it 

 appears as a clear layer under a low power ; but when examined 

 by high power it is seen that the cell processes and the processes 

 of the connective tissue (Ct.') cross through it. I cannot detect 

 fibres running in any but the perpendicular direction, so that it 

 cannot be con.^idered as a real boundary layer separating the retinal 

 elements into two divisions. I suppose it will correspond to 

 Spencer's molecular layer {l,c. PI. xvi. figs, 3-6. Mo.). 



Seventh Layer. — A layer (N"") composed of round nuclei 

 with much connective tissue. In some places the nuclei can be 

 seen to belong to columnar-like cells, but in the majority of cases 

 the cell has disappeared, and the nuclei are surrounded by con- 

 nective tissue. It is easy to see that if the columnar cells of this 

 layer were to persist, a layer of cones would be formed, such as 

 Spencer has described in some of his forms. 



In some places in the retina it appears to me that there is a 

 supporting network of connective tissue, in which the different 

 elements are embedded. I think it is highly possible that 



