362 Journal of Comparative Neurology. 



4, The noticeable reduction in the size, or the complete 

 absence of the aqueous and vitreous chambers. 



5. The varied modification in the shape and size of the 

 lens. Also the peculiar cell structure of the lense. 



All the structures of the normal mammalian eye are pres- 

 ent in some form or other. 



The two stages of the eye which were studied, the young 

 at birth and the adult, show a great similarity. The most no- 

 ticeable difference is in the size of the eye and in the develop- 

 ment of the retina. 



The eye muscles and the optic nerve are easily traced 

 back to the skull. At birth the nerve presents in its course 

 from the eye to the skull a peculiar arrangement. It is com- 

 posed of numerous cells and a few fibers. In the adult the 

 nerve fibers are much more numerous. 



The eye cleft as seen in cross sections shows the same di- 

 ameter in both vertical and horizontal sections. It meets the 

 eye at such an angle that it is impossible for rays of light, should 

 any enter, to pass into the eye along the axis of vision. 



All the elements of the normal retina are present, but, 

 owing to the much crowded condition, the ganglion cell layer 

 is much increased in thickness. 



The lens which is found in a great variety of shapes and 

 sizes is composed of large irregular cells with distinct nuclei. It 

 is therefore incapable of functioning as a normal lens. 



Considering the degenerate conditions which exist, it is ex- 

 tremely doubtful whether the eye of the mole functions in any 

 sense. At the best it can do no more than distinguish between 

 light and darkness. 



REFERENCES. 



1. True, Frederick W. A Revision of the American Moles. From the 



Proceeditigs of the U. S. National Museum, \o\. XIX, Pages 1-112, 

 1896. 



2. Sutherland, Alexander. Transactions of Royal Society of Victoria, 



1895, P- 27°- Quoted in Origin and Growth of the Moral Instinct. 

 Vol. I, page 102. 



3. Heape, Walter. The Development of the Mole (Talpa europaea). 



Quart. Journ. Micr. Sc, Vol. XXVII, p. 123-164. 



