II APPENDAGES OF CLADOCERA 41 
In the Sididae there are six pairs of thoracic limbs, which are 
nearly alike in the female; in the Bosminidae there are six pairs, 
the first two modified for prehension, the last much reduced. 
Fic. 12.—Thoracic limbs of female Simocephalus vetulus. A, The first ; B, the second ; 
C, the third; D, the fifth. Br, Bract; Hp, epipodite; Hx, exopodite; Gn, 
gnathobase. 
‘In the male, the first thoracic limb is usually provided with 
a long sensory process and a prehensible hook (Figs. 11, 19). 
In the Gymnomera the limbs are cylindrical, jointed rods, 
