230 THE ANNELIDA POLYCHAETA. 



Normally both simple and compound setae are present. The simple setae 

 are of various types, a characteristic form among the ordinary ones being a 

 very deUcate type with fine stalk and expanded terminal part distally pectinate. 

 The compound setae have the terminal piece hooked or dentate, with membran- 

 ous shields over the teeth. In the middle and posterior region uncinate spines 

 or crochets occur. 



Anal cirri two or four. 



The neplu-idia have large, open, internal funnels through which in ordinary 

 forms the sex products find exit. 



The proboscis is always armed with a powerful and complex system of horny 

 or partly calcareous plates or jaws. Of these there is ventrally a pair of man- 

 dibles and in addition seven or nine maxillae, the odd plate being normally on 

 the left side. 



A distinct sexual dimorphism exists in some species, such as Leodice norve- 

 gica and L. gigantea. A form of epitoky also occurs in some species, among which 

 are the more conspicuous representatives of the palolo worms about which 

 so much has been written, the best known of these being the Leodice viridis 

 (Grube) of the South Seas. Typical epitoky, as seen for example in the Nereidae 

 and Syllidae, is accompanied by a transformation in the parapodia and the 

 development of special natatory setae in the sexual or epitokous division of 

 the body. In the members of the present family these modifications do not 

 occur. On the contrary, in the epitokous region the setae become much reduced 

 in number and the somites undergo other special changes. At the time of sexual 

 maturity the epitokous region becomes detached from the anterior end and, leav- 

 ing the normal habitat, such as the cavities or burrows in coral reefs, rises to the 

 surface and becomes pelagic. At the surface the sexual products are discharged. 

 This swarming occurs at very definite times in relation to season and the phases 

 of the moon. The habits of the Atlantic palolo, Leodice fucata, have been 

 described by Mayer (Papers Tortugas lab., 1908, 1, p. 107, pi. 1). Cf. also 

 Moore's observations on L. paloloides of the Californian Coast (Proc. Acad, 

 nat. sci. Philad., 1909, p. 246). At the time of swarming the Atlantic Palolo 

 turns about in its tunnels in the coral and limestone, detaches the sexual division, 

 from which the products are discharged at the surface at sunrise, while the 

 head-end regenerates the posterior end. In the same category is the "wawo", 

 as known to the natives of the Malay archipelago, which is Lysidice oele, this 

 form swarming on the second and third nights after full moon in March and 

 April. {Cf. Horst, Mus. Haarlem Rumphius gedenkb. kolon., 1902, p. 105). 



