26o 



POLYCHAETA 



and in the Amphinomidae it is provided with a dorsal ridge or 

 " caruncle," which is a leaf-like process overlapping three or more 

 segments. In many Aphroditidae (as well as in Polydora) there 

 is a peculiar " frontal " ridge passing forwards from the prostomial 

 tentacle, and downwards into the mouth (Figs. 132, c,and 133,A,a;). 

 In all the Nereidiformia, as well as in Sabelliformia and 

 Chlorhaemidae, the prostomium bears sensory processes of two 

 kinds, viz. dorsal tentacles and ventral palps. The latter are in- 

 variably two in number, and are particularly well developed in 

 Aphroditidae, Nereidae, Syllidae, some of the Eunicidae, and in 



FIG. 132. Aphro- 

 dite aculeata L. 

 Ventral view of 

 anterior region, 

 x 6. a, Prosto- 

 mium ; c, frontal 

 ridge oil prosto- 

 mium ; d, neuro- 

 podial cirrus ; I, 

 lower lip ; m, 

 mouth ; p, palp ; 

 s, iutersegmental 

 groove ; t, ten- 

 tacle ; I, foot 

 of peristomium, 

 which has 

 shifted forwards 

 so as to lie in 

 front of the 

 mouth ; II to V, 

 successive feet. 



Chlorhaemidae. Even when they are apparently absent, as in 

 Nephthys, it is possible that they are represented by certain 

 lobes at the sides of the mouth, for in many Syllidae they are 

 so fused with the prostomium as to be scarcely distinguishable. 

 In the Chlorhaemids the palps 1 are grooved, and in the 

 Sabelliformia they become considerably branched, and extend 

 round the prostomium so as to nearly meet dorsally and ventrally. 

 Each palp is, in this sub-Order, represented by a greater or smaller 

 number of long, mobile filaments, arising from a common base ; 

 they are grooved along the inner side, ciliated, and provided with 

 secondary processes. The crown of "gills," in fact, is nothing 

 1 It is doubtful whether these organs are palps or only lateral lips. 



