DEGENERATE EYES IN THE CUBAN CAVE SHRIMP. 2/ t 



FIG. 4. Kye of normal shrimp ; same 

 magnification as Fig. 3. 



In the right eye, a fibrous 



strand the optic nerve ex- 

 tends from the anterior outer part 



of the ganglion forward to the 



retinal elements. The optic nerve 



is bounded on each side by a 



layer of pavement cells with 



prominent nuclei. (Fig. 5.) In 



the right eye, the retinal elements 



are spread out rather loosely in 



the form of a fan, the apex of 



which is directed toward the op- 

 tic nerve. Some spongy tissue, 



probably coagulated haemo- 



lymph, appears on each side of the 



optic nerve between the bounding 



membrane and the hypodermis. 



Comparison of Normal and Degenerate Eyes. - - Fig. 3 is from 



a photograph of the eyes 

 of the blind shrimp. Fig. 

 4 is from a photograph of 

 the author's preparation 

 of a normal shrimp eye, 

 made with the same mag- 

 nification used in Fig. 3. 

 It will be noticed (i) that 

 the degenerate eye is 

 much smaller than the 

 normal eye, (2) that its 

 optic ganglion is appar- 

 ently a single mass of 

 cells and fibers, and is not 

 divided into parts as in the 

 normal eye, and (3) that 

 the retina and dioptric ap- 

 Fig. 5. Eye of blind shrimp. 4 mm. objec- paratus are represented by 



live and 4 projection eye-piece, rf, retinula ^ meres t vestiges of 

 cells; b, optic nerve; mb. /, bounding mem- structures as they 



brane of optic nerve; A, hypodermis; ct- cor- 



neal cuticula ; d, coagulated hsemolymph. exist in the normal eye. 



