396 CRUSTACEA ENTOMOSTRACA. 



rostrum are usually many- join ted (25 in Gymrioplea) and, by 

 their powerful strokes, propel the animal by leaps through the 

 water. They are beset with olfactory structures, and in the 

 male one or both may be modified as a prehensile organ for 

 catching and holding the female (Fig. 258). They are never 

 biramous. The posterior antennae, which are always the shorter, 

 are in some families biramous (Fig. 260). In the parasitic 

 Lernaeidae and their allies, they serve as organs of attach- 

 ment to the host (Fig. 266). 



The mandibles, in the free-living forms have a toothed blade 

 (basal joint) projecting inwards on either side into the mouth, and 

 a simple or biramous (Fig. 260) palp, which however in Cyclops 

 is reduced to little more than a group of bristles (Fig. 259). An 

 upper lip projects in front of the mouth and a bilobed lower lip 

 may be present behind it. In the parasitic forms the lips are 

 produced and applied together to form a conical suctorial appara- 

 tus within which the palpless, styliform and piercing mandibles 

 are contained (Lernaeopodidae and Caligidae). In Philichthys 

 and its allies only the upper lip is produced. The first maxillae 

 lie behind and external to the mandibles, and are in the 

 Calanidae lobed structures resembling a Phyllopod appendage (cf . 

 Fig. 260). In Cyclops they are more jaw-like (Fig. 259), and in the 

 parasitic forms are much reduced, and situated on the outer sur- 

 face of the sucking tube. The second maxillae and the maxillipeds 

 are uniramous. In the free forms the maxillipeds are generally 

 the longer and the terminal portion can be folded on the basal 

 joints (the " hand " of Jurine). They are especially modified as 

 prehensile organs in the males of the Corycaeidae in which group 

 the anterior antennae are not adapted in this manner. In the 

 females of the parasitic Lernaeopodidae they are generally long 

 and arm-like, ending in a horny disc, common to the pair, by 

 which the animal is attached to the host (Fig. 264, c). 



The swimming feet consist of a two- jointed basal portion, 

 and two three -jointed, setigerous, flattened rami (Fig. 261). 

 The coxopodites of these appendages are often intimately con- 

 nected by a median plate, or " coupler," regarded by Hartog 

 as a prolongation downward of the sternite of the segment 

 (Fig. 260). In the parasitic groups the swimming feet are 

 much reduced, and in some entirely absent. In several free 

 forms while the anterior swimming feet are well developed 



