TURBELLARIA : PLANARIANS. 



625 



of the body, is surrounded by a circular Sucker that is applied to 

 the living surface from which the animal draws its nutriment ; 

 and the buccal cavity 



(b) opens into a Fig. 326. 



short (Esophagus 

 (c), which leads at 

 once to the cavity 

 of the Stomach. 

 In the true Plana- 

 rim the mouth is 

 furnished with a 

 sort of long funnel 

 shaped Proboscis ; 

 and this, even when 

 detached from the 

 body, continues to 

 swallow anything 

 presented to it. 

 The cavity of the 

 Stomach does not 

 give origin to any 

 Intestinal tube, nor 

 is it provided with 

 any second orifice ; 

 but a large number 

 of ramifying Canals 

 are prolonged from 

 it, which carry its 

 contents into every 

 part of the body. 

 This seems to render 

 unnecessary any sys- 

 tem of vessels for 

 the Circulation of 

 nutritive fluids ; 

 and the two prin- 

 cipal Trunks, with 

 connecting and 

 ramifying branches, 

 which may be ob- 

 served in them, are 

 probably to be re- 

 garded in the light 

 of a Water-Vascular 

 system, the function 

 of which is essen- 

 tially Respiratory. Both sets of Sexual organs are combined in the 

 same individuals ; though the congress of two, each impregnating the 



s S 



Structure of Polycelis levigatus (a Planarian 

 worm) : — a, Mouth, surrounded by its circular 

 sucker ; b, Buccal cavity ; c, (Esophageal orifice; 

 d, Stomach ; e, ramifications of Gastric Canals ; 

 /, Cephalic Ganglia and their Nervous fila- 

 ments ; g, g, Testes ; h, Vesicula seminalis ; 

 i, male genital canal ; k, k, Oviducts ; I, dila- 

 tation at their point of junction ; m, Female 

 genital orifice. 



