174 



ZOOLOG Y. 



feet are jointed, thus anticipating the jointed appendages of 

 the Crustacea and Insects. 



The Annelides are divided into two suborders. The first 

 suborder, Oligoclmta, comprises Lumbricus, Nais, etc., while 

 the second suborder, Chcetopoda, embraces Syllis, Autulytus, 

 Nereis, Polydora, Aphrodite, and Polynoe, which are free- 

 swimming, while the tubicolous worms which respire by spe- 



FIG. 123. FIG. 123. 



Fig. ISi.Cistenides Gmtldii, and its tube. After Verrill. 

 Fig. IHS.Euchone elegans, enlarged. After Verrill. 



cial branchiae, or gills, on the head, live in tubes of sand or 

 in limestone shells. Those which live in sand or mud-tubes' 

 are Cirratulus (Fig. 124), Clywene and Clymenella (Fig. 120), 

 which has no branchiae, Amphitrite (Fig. 121), Terebrelht, 

 Cistenides (Fig. 122), Habella, and Enchone (Fig. 123), 

 while Frotula, Filof]rana, Serpula, and Sjiirorbis secrete 

 more or less coiled limestone tubes. The large solid shells 

 of the Serpulae assist materially in building up coral reefs, 



