146 
A PRELIMINARY ReEpoRT ON THE EyE oF THE Moe (Scarops 
AQUATICUS MACHRINUS). 
By JamMEs ROLLIN SLONAKER. 
It is a general belief with many people that the mole does not have 
eyes. This is possibly due to the fact that the eyes are not readily 
seen and that an animal living habitually in the ground would have little 
or no use for organs of sight. But this, like many other common ideas, is 
wrong, for the mole has not only a well-defined eye, but one which is 
readily observed on parting the fur at the right place. It is seen as a dark 
area covered by the skin and true eyelids. The latter, however, are rudi- 
mentary and the cleft between them so small that it is practically never 
open enough to admit light. (Fig. 1.) 
From this fact alone one could safely conclude that the power of sight 
in the mole is no more than to distinguish between light and darkness. 
But when the eye itself is examined this conclusion is well substantiated. 
Comparing the mole eye with a normal mammalian eye it is found to 
be quite degenerate. The stages of degeneration seem to be in the follow- 
ing manner: 
The eye decreases materially in size. This reduction diminishes the 
size of the aqueous and vitreous chambers until in some eyes they are 
wholly wanting. This allows the retina to collapse, causing the inner 
layers to become more or less jumbled together. Each of the layers may, 
however, be made out as is shown in Figs. 2 and 3. 
The lens is much modified in size and shape in different eyes. Owing 
to the great diversity of pressure exerted by the shrinking eye the lens 
takes a variety of forms which may be decidedly different in eyes taken 
from the same animal. This is shown in Figs. 2 and 3, representing the 
right and left eye respectively, from the same animal. On magnifying 
the lens the cells are seen to resemble cartilage more than typical lens 
cells. (Figs. 4 and 5.) The histological degeneracy of the lens has thus 
gone much farther than one would at first suspect. 
Ritter’ and Rabl’, in describing the development of the mole lens say 
gi O- Ritter, Die Linse des Maulwurfs. Arch. f. Micr. Anat. u. Entwl., Bd. 53, Heft III, 
p. 897. 
* Carl Rabl, Ueber den Bau und die Entwicklung der Linse. Zeitschr. f. Wis. Zool., Bd. 
67, Heft 1, 1899, p. 63. 
