Slonaker, Eye of the Mole. 351 



rate as the eye. It enters the optic nerve about .2 mm. from 

 the eye and passes forward between the nerve fibres until it 

 reaches the posterior surface of the lens. Here it branches 

 and spreads out over the posterior surface of the lens and over 

 the surface of the retina. The finer branches penetrate the 

 retina and ramify between the retinal elements as far out as tl)e 

 outer boundary of the inner nuclear layer. 



The lens of the adult mole is in many respects similar to 

 that of the young at birth. It, however, presents a marked 

 difference in form and size. The shape is by no means con- 

 stant. It varies so much that no two eyes are likely to have 

 the same form of a lens even though they come from the same 

 animal. The anterior surface is generally much more regular 

 in contour than the posterior (Plates XIX and XX). The 

 shape varies from an almost spherical lens as seen in Fig. 23 to 

 the very irregular form as represented in Fig. 25. A regular 

 form as shown in Figs. 13, 14 and 26 is the exception. The 

 shape which is most common is that of a cone as seen in Figs. 

 15 and 18. In one adult I found that each eye had a very 

 irregular and degenerate lens (Fig. 9 and 10). The lens cells 

 filled only a portion of the lens capsule and formed a very 

 irregular mass. In this case the degenerate condition could 

 scarcely be attributed to a lack of development of the lens 

 cells due to pressure or want of room. 



In two other adult moles I found each lens peculiarly 

 formed (Fig. 19, 20 and 21). In each of these the lens was 

 almost divided into two unequal parts ; a smaller anterior and a 

 larger posterior part. The two parts were in close contact, the 

 union being almost that of a plane. On close examination I 

 found that these parts were not wholly separated, but were 

 united by a small pedicel of cells (Fig. 20 and 21). These 

 uniting cells were elongated and resembled typical lens cells 

 more than any which I had found. The remaining cells, how- 

 ever, were very similar to the cartilage-like cells described in 

 the young. I am unable to give a reason for this odd shape. 

 I have found such a condition in only two animals out of prob- 

 ably one hundred which have been examined. 



