120 



ERNEST CARROLL FAUST. 



cup is a spherical body, barely touching the pigment granules, 

 opalescent, and containing within it an oval nucleus. This 

 spherical body is the enlarged nerve-cell ending with its nuclues. 

 The nerve may be clearly traced out of the mouth of the pigment 

 cup where it merges into the dorsal branch of the nerve trunk 



FIG. i. Dorsal view of the central nervous system of Cercaria pelhtcida Faust, 

 showing paired lateral and cyclopean eye-spcts and their connection with the 

 dorsal nerve trunks, ad, anterior dorsalis; al, anterior lateralis; av, anterior 

 ventralis; br, ganglion cells; le, lateral eye; me, cyclopean eye; pd, posterior 

 dorsalis; pi, posterior lateralis; pv, posterior ventralis. X 660. 



(Fig. 2). Thus the end organ of this nerve is imbedded in the 

 center of the pigment cup. In the mature cercaria the eye-spot 

 is sunken beneath the basement membrane. 



The above description holds likewise for the pigmentless 

 eye-spot, except that in this type of organ no pigment is present. 

 It is recognized in the living cercaria as a round milky body 

 slightly whiter and less transparent than the surrounding paren- 

 chyma cells. In stained material its nucleus is conspicuous and 

 its connection with the main nerve center can be made out. 

 In Cercaria pellucida although there are ganglion cells scattered 

 superficially along the main nerve trunks no cell is found at 

 the base of the cup. The pigment cup varies in shape from 



