174 



ZOOLOGY. 



feet are jointed, thus anticipating the jointed appendages of 

 the Crustacea and Insects. 



The Annelides are divided into two suborders. The first 

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

 the second suborder, Chcetopoda, embraces Syllis, Autolytus, 

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

 swimming, while the tubicolous Avorms which respire by spe- 



FlG. 122. 



Fig. 122. Cistenides Gouldii, and its tube. After Verrill. 

 Fig. 123. Euchone elegans, enlarged. After Verrill. 



FIG. 123. 



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), Clymene and Clymenella (Fig. 120), 

 which has no branchiae, Ampliitrite (Fig. 121), Terebrella, 

 Cistenides (Fig. 122), Sabella, and Euclione (Fig. 123), 

 while Protula, Filograna, Serpula, and Spirorbis secrete 

 more or less coiled limestone tubes. The large solid shells 

 of the Serpulffl assist materially in building up coral reefs, 



