38 Journal of Comparative Neurology. 



nears the caudal portion of the body it becomes more and more 

 attenuated. This attenuation is probably due to the giving off 

 of nerves to the neighboring parts. 



The entrance to the mouth of these creatures is fringed 

 with hairs. These hairs, I am inclined to think, function as sen- 

 sory setae. This view is supported by the fact that these hairs 

 rest upon a layer of elongated cells [fig. 4] which have, in well 

 stained preparations, large clear nuclei and small densely colored 

 nucleoli — cells that are innervated by the intra-oesophageal gan- 

 glion and whose general appearance indicates that they are ner- 

 vous in function. 



The most conspicuous sense organ of the genus Cypns is 

 the eye. This is a tripartite structure [fig. 2]. It consists of 

 a median and two lateral portions. The median portion lies 

 further ventrad than the two lateral. The space between these 

 three portions is liberally supplied with pigment. Each of the 

 three divisions of this so-called pigment spot is multicellular. 

 In the lateral portions the cells are as long as the structure is 

 wide, and they are arranged with their longitudinal axes perpen- 

 dicular to that section of the eye. In the median portion the 

 cells are arranged radially. The median eye of the Copepoda, 

 according to Grenadier, is, in all essentials, similar to the eye 

 above described. In describing that eye, Lang^ considers the 

 three divisions to be retinal cells. In that connection he says, 

 in describing the tripartite eye of Calanclla mcditcrranca : 

 "Each single eye is composed of a pigment cup and a strongly 

 refractive transparent 'lens' laid in and on it. The term lens 

 is, however, not applicable. It is composed of several cells, 

 each of which is connected, whether at its outer or inner side is 

 not yet certain, with a fibre of the optic nerve, and must, there- 

 fore be considered as a retinal cell." 



In Cypns Jienicki the nerve fibres are united to the outer 

 ends of the cells. This agrees with what Dr. Claus found to be 



'Op. cit., p. 352. 



