8TEEELMINTHA. 



95 



of reproduction we find a mani- 

 fest analogy with higher classes in- 

 dicated in the complete separation 

 of the sexes, which we now for 

 the first time meet with, the ovig- 

 erous and impregnating organs be- 

 ing found in separate and distinct 

 individuals. 



The Echinori/nchus gigas is the 

 species which has undergone the most 

 complete investigation,* and will 

 serve as an example of the usual 

 structure of the Acanthocephala. 



(126.) The Echinorynchi inhabit 

 the intestinal canal of various ani- 

 mals, to the walls of which they fasten 

 themselves by a singular contrivance. 

 In the animal under consideration, 

 which is found in the intestines of 

 the hog, the head (a, fig. 41 ; 1, 2, 

 3) is represented by a retractile pro- 

 boscis, armed externally with four 

 circlets of sharp recurved hooks, 

 which, when plunged into the coats 

 of the intestine, serve as secure an- 

 chors by which the creature retains 

 itself in a position favourable to the 

 absorption of food. In Jig. 41, 1, 

 2, this aculeated proboscis is repre- 

 sented of its natural size relative to 

 the body of the entozoon, as it ap- 

 pears when fully protruded ; but, 

 when not in use, the spinous part 

 is retracted, and concealed by the 

 mechanism, of which an enlarged 

 view is given at Jig. 3. When 

 extended, the position of the organ 

 is indicated by the dotted lines ; 

 but in the drawing the whole or- 

 gan is represented as drawn inwards 



* Cloquet, Anatomie des Vers intestinaux. 



Fig. 41, 



\rv 



R 



Paris, 1824. 



