208 



THE ANATOMY OF INVERTEBRATED ANIMALS. 



FIG. 54. Protula Dysteri. A, the sexual, mature animal, extracted from its calca- 

 reous tube : a, branchial plumes ; 6, hood-like expansion of the anterior end of the 

 body ; c, the mouth ; $, the stomach ; 6, the anus ;/, the testes ; g, the ova. J3, 

 a Protula in course of proliferation; &, the branchiae of the zoSid. 



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, 



