CALANELLA— LIMULUS. 



159 



of Calanella are very remarkable, and, indeed, but for 

 their position and the presence of pigment, would 

 hardly be recognized as eyes. They are three in 

 number, and together form an X-shaped body (Fig. 108), 

 supplied by a large nerve (iVIop.), and consisting of 

 three groups of large nerve-cells, embedded in pig- 

 ment. There are eight in each of the two side groups, 

 and ten in the central. In form they are pear-shaped, 

 with the narrow end turned towards the nerve. The 

 organ contains no lens nor rods. 



Fig. 108.— Eyes of Calanella Mediterranea (after Gerstarker). Pg., pigment cells; 

 N.fr., frontal nerves; N.op., nervus opticus. The numbers show the numbers 

 of the cells. 



The eyes of the king crab (Limulus) have been 

 described by Grenacher and by Lankester and Bourne.* 

 The two lateral eyes form a polished, kidney-shaped 

 protuberance on each side of the great shield. The 

 outer side is smooth, but on the inner surface it is 

 produced into a number of conical processes (Fig. 109), 



* " On the Eyes of Scorpio and Limulus," Quarterly Journal of 

 Microscopical Science, 1883. 



