MUSEUM OF COMPARATIVE ZOOLOGY". 69 



number of cells which cover the area of each cone is about twelve. A 

 corneal hypoderrais of this same character also occurs iu Talorchestia, 

 although iu this instance the number of cells over a cone is only about 

 nine. 



According to Watase ('90, p. 295), in the species of Talorchestia 

 which he studied there were only two cells in the corneal hypodermis 

 opposite each cone, or, as he expresses it, under each facet. When com- 

 pared with the results recorded in the preceding paragraph, this observa- 

 tion appears somewhat striking, and the more so since two, the number of 

 cells recorded, is the usual number found under each facet in other Crus- 

 taceans. If Watase's observation be correct, the relation which would 

 thus be established between this Amphipod and other Crustaceans would 

 be an interesting: one. The desirability of confirming Watase's observation 

 must, therefore, be evident ; but unfortunately he has not given the name 

 of the species of Talorchestia which he studied, and I have therefore 

 not been able to verify his statement. Iu the only species of this ge- 

 nus which I have examined, viz. T. longicornis, the arrangement of the 

 cells in the corneal hypodermis is very different from that described 

 by Watase. 



The conclusions which I draw from the preceding account are, that 

 in'the eyes of Amphipods a corneal hypodermis is present, and the cells 

 composing it are usually not arranged with regularity. 



The peculiar bodies observed by Schmidt ('78, p. 5) in the membrane 

 between the corneal hypodermis and the retina proper in Phronima, and 

 considered by Claus ('79, Taf. VI. Figs. 48, 49, B. mi.) as nuclei, are 

 apparently not represented in other Amphipods. Their significance is 

 still a matter of doubt. 



The corneal cuticula in Amphipods has been described by almost all 

 observers as unfacetted. 1 According to Delia Valle ('88, p. 94), how- 

 ever, in some of the Ampeliscidse this cuticula is facetted, and Watase 

 ('90, p. 295) has also observed facets in Talorchestia. But with these 

 two exceptions the corneal cuticula of Amphipods has been described 



1 An unfacetted corneal cuticula has been recorded in the following genera of 

 Amphipods : Amphithoe (Milne-Edwards, '34, p. 116) ; Caprella (Frey und Leuck- 

 art, '47 a , p. 103) ; Cynnvis (Miiller, '29, p. 58, Frey und Leuckart, '47, p. 205) , Gam- 

 marus (Miiller, '20, p. 57, Frey und Leuckart, '47, p. 205, Pagenstecher, '61, p. 31, 

 Sars, '67, p. 61, Leyriig, '78, p. 235, Grenacher, '79, p. 109) ; Hyperia (Gegenbaur, 

 '58, p. 82, Grenadier, '79, p. Ill, Carriere, '85, p. 160) ; Phronima (Pagenstecher, 

 '61, p. 31, Schmidt, '78, p 5, Claus, '79, p. 131 ) ; Talitrus (Grenacher, '79, p. 109) ; 

 and the Plntjisce.hdai (Claus, '87, p. 15). I have observed an unfacetted corneal 

 cuticula in Gammarus, Caprella, and Talorchestia longicornis. 



