208 THE ANATOMY OF INVERTEBRATED ANIMALS. 



Fig. hi.—Protula Bysteri. A, the sexual, mature animal, extracted from its calca- 

 reous tube : a, branchial plumes ; 6, hootl-likeexijansiou ol the anterior end of ihe 

 body: c, the mouth; d, the stomach; e, tlie anus ;/, the testes ; g, the ova. B, 

 a PiOtula in course of proliferation ; 6, the branchiae of the zo6id. 



body, and its walls are very thick and muscular. At its an- 

 terior extremity it is surrounded with a circle of small papil- 

 lae, immediately behind which are four strong, pointed and 

 curved horny teeth, implanted in the muscular wall (Fig. 52, 



