POLYZOA. 



73 



upper surface. The statoblasts (Fig. 21, D) are circular, provided 

 with a zone of air cells, and with hooked spines, the total diameter 

 beina: about J77 of an inch. 



Sub-class II. — Entoprocta, 



In this small group, both orifices of the alimentary canal open 

 within the circle of tentacles, and there is no tentacular sheath. 



The polypides are borne on contractile stalks. In the Pedicel- 

 linidcB the stalks arise from a creeping stolon. In Pedicellina cernua * 

 (Fig. 24) a stolon, creeping over sea-weeds, etc., gives rise to stalked 

 cups, the movements of which are vigorous : "the polypides, when 

 excited, dash themselves vehemently from side to side. The heads 



Table 

 Case A, 

 upright 

 part. 



Pedicellina cernua. X 27. 

 [' The Cambridge Natural History.'] 



are easily knocked off, but the decapitated stalks develop fresh ones." 

 In Ascopodaria the stalks are swollen at the base ; A.frnticosa*, from 

 Port Phillip, Victoria, forms beautiful tree-like colonies. The 

 LoxosomidcB do not form colonies, owing to the buds becoming 

 detached from the parent. The species of Loxosoma are always found 

 associated with some other animal, such as a worm or Tunicate. 

 The tentacles of the polypide are arranged obliquely to the long 

 axis of the body, hence the name of the family (loxos, oblique). 

 Loxosoma phascolosomatum* occui's, in the form of delicate tufts, on 

 the caudal end of the Sipanculid worm Fhascolosoma. The individuals 

 resemble pins with little white heads, and are capable of vigorous 

 movements to and fro ; occasionally a stalk coils itself up into a 

 spiral. 



