34 Journal of Comparative Neurology. 



In Cypris herricki Turner the nerve fibres are united to the 

 outer (peripheral) ends of the retinal cells. This agrees with 

 what Dr. Claus found to be the state of things in the eyes of 

 the Copepoda, Clodocera and Ostracoda examined by him [7]. 



There is a striking resemblance between the triune eyes of 

 the Ostracoda and those of the Copepoda. In describing the 

 compound eye of Calanella mediterranca. Dr. Grenacher remarks 

 *' Each eye is composed of a pigment cup and a strongly re- 

 fractive transparent ' lens ' laid in and on it. The term lens is, 

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

 o{ which is connected, whether at its outer or inner side is not 

 yet certain, with a fibre of the optic nerve, and must therefore 

 be considered as a retinal cell." Since the superficial resem- 

 blance between the Ostracod eye and the Copepod eyt is so great, 

 one is apt to conclude that the above words of Dr. Grenacher 

 might be applied to the Ostracod eye. Against such an assump- 

 tion I desire to enter a most emphatic protest. As stated above, 

 in the eye of Cypris we find both retinal cells and lenses, and 

 the two structures are histologically quite distinct. On the out- 

 side of the eye, covering lens and all, there is a nucleated epi- 

 thelial layer [fig. 2]. 



Since the publication of the paper ^ in which O. Biitschli 

 attempts to show how the lateral eyes of the vertebrates may 

 have been derived from the median tripartite eye of Salpa, this 

 tripartite eye, which is of almost universal occurrence among 

 the entomostraca, becomes enhanced in interest. One at once 

 begins to speculate on the possibility of this median triune eye 

 of the entomostraca becoming transformed into the lateral eyes 

 of the higher Crustacea. Indeed, in his late work, Dr. Claus ^ 

 has already stated that the lateral eyes of the Corycaeidae are 

 laterally rotated portions of the median eyes. In this connec- 

 tion it may be of interest to quote a portion of Dr. Giesbeck's 



1 Einige Bemerkungen ueber die Augen der Salpen, Zool. Anz., XV., 

 Jahrg. 349. 



2 Ueber die feineren Bau des Medianauges der Crustaceen. Anzeigtr Akad. 

 Wien. 1891, pp. 124-127. Ref. in Zool. Jahrsbericht {\\x 1891, Arthropoda, 29. 



