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 ; d, the stomach ; e, the anus ;/, the testes ; g, the ova. B, 

 a Protula in course of proliferation ; 6, the branchiae of the zo5id. 



bod}', 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, 



