Turner, Nervous System of Cypris. 33 



Careful search has not yet revealed a sympathetic nervous 



system. 



Sense Organs. 



Compound Eye. — The most conspicuous sense organ of the 

 genus Cypris is the compound eye. When viewed from above, 

 this eye usually resembles a quadrilateral pigment spot [fig. 36]. 

 In Cyclocypris and Cypria, this eye is quite large and the pigment 

 is intensely black ; in Cypris and Cyprinoti/s, the eye is of medi- 

 um size ; in Candona, the eye is inconspicuous and the pigment 

 is reddish ; while in TypJilocypris, according to Wenzel Vavra, 

 there is no eye in the adult. The eye of the embryonic Typhlo- 

 cypris, according to the same author, becomes metamorphosed 

 into an inconspicuous non-optical sense organ. 



This eye is a triune structure. It consists of a median and 

 two lateral portions, each of which is supplied with a lens 

 [fig. 2]. The lens of the median portion is on the front aspect 

 [fig. 36], while the lenses of the lateral portions are on the 

 sides [fig. 2, 36]. This median compound eye, which lies in 

 about the same vertical transverse plane as the supra-oesopha- 

 Sfeal gfana;lion, is located where the dorsal border of the animal 

 is united to the dorsal portion of the shell. Hence there are two 

 planes, at right angles to each other, that pass through both the 

 compound eye and the supra-oesophageal ganglion. These 

 two planes are the mesal and a transverse plane. 



Histologically there are five parts to this compound eye : 

 lens, retina, pigment, superficial epithelium, nerve [fig. 2]. 

 Corresponding to each of the three divisions of the eye we 

 have a retina and a lens [fig. 2] and a nerve. The pigment is 

 deposited between and around the retina. The retinas are cell- 

 ular structures, the cells being arranged with their longest axis 

 perpendicular to the outer surface of the retina [fig. 2]. Each 

 retina is supplied with a lens, and these are always on the outer 

 surface. In the lateral portions these lenses are on the side, 

 while in the median the lens is on the front aspect [fig. 36]. 

 The median portion lies lower than the lateral. Excepting the 

 central portions of the lenses, all of the surface of the eye, as 

 well as the space between the retinas, is pigmented [fig. 2, 36]. 



