570 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Plate LIV. 



FiOr. 200. Ommatidium of eyeof small adult Alpheus xaulcyi (from brown spongre) ; pigment removed 



by nitric acid. x2i)4. 

 Figs. 201-20i. Transverse sections through four adjacent ominatidia of first larva of same. In Fig. 



201 the corneageu is cut, and in Fig. 2(»2 the nuclei of the cone mother cells. In Fig. 



204 the rhabdoni is sectioned and the seven jiroximal retinular cells. x294. 

 Figs. 205-208. Transverse sections through adjacent ommatidia of the adult eye, taken at various 



levels. Fig. 205, the deepest secrtion, shows the peculiar seven-pronged tigure of the 



rhabdom. The proximal retinular cells a|>pear in sections, as if fused together, x 294. 

 ViGH. 209-211. Transverse serial sections through the first larva of Alpheiis saulcyi. •x74. 



REFERENCE LETTERS. 



A. /, first aiiteuna. 

 A. II, second antenna. 

 a.C})., accessory pigment cell. 

 ac.pii., nucleus of accessory pignient cell. 

 ao., ear. 



Bin., intercepting or basement momhrane. 

 CO., crystalline cone cells. 

 eg., corneagen. 

 cl., lens. 



Co., CO., crystalline cone. 

 cmh., cone membrane. 

 hd., hypodermis. 



me., membrane of distal retinular cells. 

 nf., nerve fibers, 

 oc, ocellus. 



og., optic ganglion. " 



of., optic enlargement of brain. 

 pap., papilla of ocellus. 

 p.g.c, distal retinular cells, 

 /i'., rostrum. 

 lib., rb., rbabdoin. 

 Ket., retina. 

 rtl., proximal retinular cells. 



