Slonaker, Eye of the Mole. 337 



After imbedding in paraffin sections were made 5, 10 and 15 

 micra thick. 



Several fixing agents were used, but those which proved 

 most valuable were Perenyi's fluid, Potassium bichromate and 

 10% Formalin. Saturated solution of Bichloride of Mercury, 

 10% Nitric Acid, Absolute Alcohol, 50% Alcohol and Platino- 

 aceto-osmic mixture were used with poor success. Perenyi's 

 fluid usually preserved the eye in the best general shape, but is 

 not good for the finer histological study. 10% formalin or 

 potassium bichromate gave much better histological prepara- 

 tions. The latter, however, generally caused the retina to 

 separate from the choroid and pigment layers. 



Staining was done wholly on the slide. The following 

 stains were used with good success. Ehrlich-Biondi, Wei- 

 gert, Minot's (23) Haematoxylin Method, Haematoxylin and 

 Eosin, and Haemalum. 



All the figures are semi-diagrammatic camera drawings. 

 The outlines and the principal structures were sketched with 

 the aid of the camera. 



Stages Investigated. 



Owing to the difficulty of procuring the embryos I have 

 succeeded in studying but two stages in the development of the 

 mole's eye: (i) The eye of the young at birth; and (2) the 

 eye of the adult. Very little difference is noticed between 

 the young and the adult. The most marked difference is a 

 slight increase in size. The different conditions I will describe 

 in detail later. 



The difficulties which present themselves in obtaining 

 material for the embryonic stages are not at first appreciated. 

 As is well known, the mole hibernates late in the fall and spends 

 its winter in nests and burrows from two to three feet below 

 the ground. This depth is always below the region of frost 

 and would thus vary in different localities. 



In southern Indiana the young are born some time in 

 March, generally before the adults come to the surface. One 

 adult female containing three young was caught on the third of 



