THE EYE OF CRYPTOBRANCHUS. 



ALBERT M. REESE. 



Since no investigations, apparently, have been made on the 

 anatomy of the eye of the American giant salamander, C. alle- 

 gheniensis, a brief description of that organ may be of interest. 



In the living animal the eyes are quite inconspicuous, due to 

 their small size, their lack of bright coloration, and to the wrinkled 

 condition of the skin that surrounds them. The pupil, as seen 

 from the surface, is very irregular in outline ; it appears as a small, 

 jagged, black spot in the center of the gray iris. The eyes of 

 the living Cryptobranchus do not differ markedly in appearance 

 or relative size from those of Nectitms. 



In order to study their structure, the eyes, with a little of the 

 surrounding tissue, were removed and sectioned in colloidin. 

 Owing to the hardness of the lens it was not possible to cut very 

 thin sections. The tissue was stained in toto with borax carmine, 

 and after the sections were arranged serially on the slides they 

 were stained with Lyon's blue. The memorandum as to fixation 

 having been lost, it is not possible to give the method, but the 

 results were fairly satisfactory except in the case of the layer of 

 rods and cones of the retina. The figure represents a section 

 through the middle region of the eye, passing through the optic 

 nerve and the pupil. 



The sclerotic coat (Sc] is rather indefinite in extent, and is 

 largely chondrified. This cartilage forms a very thick capsule 

 that surrounds considerably more than half of the globe of the 

 eye. It is perforated, of course, at the back for the passage of 

 the optic nerve. The walls of the cartilaginous capsule are not 

 of homogeneous structure throughout, but are penetrated at 

 places by ingrowths of tissue apparently derived from the choroid 

 (Ig). The unchondrified portion of the sclerotic is, as has been 

 said, of rather indefinite amount. It extends in front of the eye, 

 between it and the superficial epithelium, to form a comparatively 

 thick and, one would think not very transparent, cornea (C). In 

 the fibrous portions of the sclerotic, as in other parts of the 



