474 SLONAKER. [Vol. XIII. 



Human and Gorilla. 



The fovea and macula lutea are readily seen, located about 

 4 mm. toward the nasal side of the entrance of the optic nerve. 

 The macula is rather sharply marked off from the surrounding 

 retina, and is of small extent compared with other mammals. 

 The blood-vessels in either of these cases were not injected, 

 but they could be traced as far as represented in PL XXVII, 

 Figs. I, 2. Figs. 24, 25, PL XXVIII, represent horizontal sec- 

 tions through a child's eye and an adult's respectively. The 

 foveola described by Dimmer (29) is much more noticeable 

 in the adult (Fig. 25) than in the child's fovea. In the case of 

 the gorilla, which was about nine hours post mortem, folds had 

 formed about the fovea so that its appearance is not well rep- 

 resented in sections. PL XXVIII, Fig. 26, represents the 

 horizontal section and Fig. 27 the vertical section through 

 the center of the fovea. 



Rabbit (Lepus sylvaticus). 



The nerve entrance is readily seen above the center and a 

 little toward the temporal side. From it two large bundles of 

 nerve fibres branch out horizontally. In the injected specimen 

 the blood-vessels are seen to lie in these bundles, and do not 

 branch over the rest of the retina. The band-like area is seen 

 to extend horizontally across the retina, immediately below the 

 nerve entrance, and to gradually fade out just before reaching 

 the ora serrata. It is from J^ to i mm. broad (PL XXVII, 

 Fig- 13)- 



Rat (Mus rattus). 



I have not succeeded in demonstrating the presence of a 

 definite area in this animal. 



WoODCHUCK (Arctomys monax). 

 Red Squirrel (Sciurus hudsonicus). 

 Fox Squirrel (Sciurus niger). 

 Chipmunk (Tamias striatus). 



No area is visible to the naked eye, but in horizontal and 

 vertical sections a slightly thicker oblong or oval area is dis- 



