II APPENDAGES OF PHYLLOPODA 25 
plates as in Chirocephalus (Fig. 2), or minute vestigial fila- 
ments as in Apus, in which genus Zaddach, Huxley, and Claus 
have all failed to find any trace of a second antenna in some 
females. In the male Branchipodidae the second antennae are 
modified to form claspers, by which the female is seized, the 
various degrees of complication which these claspers exhibit 
affording convenient generic characters. In Branchinecta each 
second antenna is a thick, three-jointed rod, the last joint 
forming a claw, while the 
second joint is serrate on its 
inner margin; in branchipus 
the base is much thickened, 
and bears on its inner side 
a large filament (perhaps 
represented by the  proxi- 
mal tubercle of Branchinecta 
and Artemia), which looks 
like an extra antenna. In 
Streptocephalus the terminal 
joint of the antenna is bifid, 
and there is a basal filament 
hke that of Branchipus , 
in Chirocephalus diaphanus 
(Figs. 5, 6) the main branch 
of the antenna consists of 
two large joints, the terminal 
joint being a strong claw with 
a serrated process at its base, 4 a es Sed 
; : er Fic. 6.—Chirocephalus diaphanus. Second 
while the proximal Jot antenna of male, uncoiled. 
bears two appendages on its 
inner side; one of these is a small, subconical tubercle, the second 
is more complicated, consisting of a main stem and five outgrowths. 
The main stem is many-jointed and flexible, its basal joint being 
longer than the others, and bearing on its outer side a large, 
triangular, membranous appendage, and four soft cylindrical 
appendages, the main stem and its appendages being beset with 
curious tubercles, ending in short spines, whose structure is not 
understood. Except during the act of copulation this remarkable 
apparatus is coiled on the inner side of the antennary claw, the 
jointed stem being so coiled that it is often compared to the 
