GENERAL ANATOMY. 11 



it is equal in size to the primary branch, and may be 

 numerously jointed (Longipedia, Calanidce, Misoph- 

 riidce). In Cyclopida} the secondary branch is want- 

 ing, and in most of the Harpacticidce it is reduced to 

 small dimensions or, in some few cases, is quite absent. 

 The limb is generally curvate, dilated at the apex, and 

 provided with numerous curved or geniculated setse at 

 the extremities and over the margins of both branches. 

 In the PcBcilostoma and Siphonostoma it consists of 

 only one branch, which in the male of the Corycceidce 

 (Plate LXXXIII, figs. 13, 14) is powerfully clawed, 

 and is used chiefly as a prehensile and clasping 

 organ. 



The mandible consists, in its fully developed form, 

 of a masticating portion and a " palp ;" the first-named 

 division is in the form of an elongated, more or less 

 triangular plate, dilated at the distal extremity and 

 cut up into a variable number of tooth-like processes, 

 these being sometimes only slight serrations, some- 

 times large and powerful. The palp is variously 

 formed ; in the Calanidce, most of the Harpacticidce, 

 and in many Cyclopidce, it is composed usually of a 

 large basal joint, from which spring one or two 

 small setif erous branches ; these branches are generally 

 1- or 2-jointed, but may be absent altogether. In the 

 sub-families Porcellidiince and Idyince the setiferous 

 portions of the organ are very largely developed, form- 

 ing large laminated appendages, which are fringed 

 with densely ciliated filaments (Plate LXVIII, fig. 4 ; 

 Plate LXIX, fig. 11). In the genus Cyclops, while 

 the biting part of the mandible is well developed, 



