70 BULLETIN OF THE 
as smooth. The absence of facets from Amphipods is naturally ac- 
counted for by the absence of a definite arrangement among the cells 
of the corneal hypodermis. 
In the genus Tenais, the systematic position of which is probably 
somewhere between the Amphipods and Isopods, the corneal cuticula is 
stated by Miller (’64, p. 2) to be facetted, at least in the males. Ac- 
cording to Blane’s (83, p. 635) more recent observations, however, it is 
claimed to be unfacetted. 
The cones in Amphipods have long been known to be segmented. 
The number of segments of which each cone is composed has been dif- 
ferently stated, however, by different observers. According to Clapa- 
rede (60, p. 211), the cones in Hyperia are each composed of four seg- 
ments. This also is the number given by Sars (’67, p. 61) and by 
Leydig (79, p. 235) for Gammarus. Both Hyperia and Gammarus 
have since been carefully studied, and these observations are now 
known to be inaccurate. Claparede was perhaps influenced in his 
statement by his belief that all cones were composed of four cells. 
Sars was probably misled by the supposed fact that in Gammarus the 
cone is surrounded by four bands of pigment, which sometimes give it 
the appearance of being divided into four segments. 
The actual number of segments in the cone of Amphipods is two. 
This number was first recorded by Pagenstecher (’61, p. 31) for the 
cones of Phronima. Pagenstecher believed, however, that the cones 
in this Crustacean increased in numbers by division, and that they 
showed no indication of being composed of two segments except when 
they were undergoing this process. I need scarcely add that subse- 
quent investigations have not confirmed Pagenstecher’s belief. Cones 
composed of two segments have been observed in some six or seven 
genera of Amphipods.? 
The retinula in Amphipods is stated by different observers to consist 
of either four or, five cells. Five have been seen by Grenacher (’74, 
p- 653) and Carriere (85, p. 160) in Hyperia; by Grenacher (’79, 
p- 112), Claus ('79, Taf. VIII. Fig. 65), and Carriere (85, p. 164) in 
Phronima; and by Mayer (’82, p. 122) in Caprella. 
In Gammarus, Sars (67, p. 61) observed that the cone had four 
1 Jn Caprella (Mayer, ’82, p. 122), in Gammarus (Grenacher, 779, p. 110, Car- 
riére, ’85, p. 156), in Hyperia (Grenacher, 74, p. 652), in Oxycephalus (Claus, 71, 
p- 151), in Phronima (Schmidt, ’78, p. 5, Grenacher, ’79, p. 112, Claus, ’79, p. 130), 
in Talorchestia (Watase, ’90, p. 296), and in the Platyscelide (Claus, ’87, p. 15). 
In Gammarus ornatus, Talorchestia longicornis, and Caprella, each cone is composed 
of two cells. 
