148 



HELMINTHOZOA. 



Fig. 74. 



A 



and the same unity, or constitute such a 

 unity ; and this is doubtless the case with 

 the animals we are now considering. 



(390.) The ACANTHOCEPHALA*, called 

 likewise ECHTNORHYNCHI, constitute a 

 distinct group of Helminthozoa, distin- 

 guished by the remarkable armature of 

 their oral apparatus, as well as by the 

 peculiarities of their internal organiza- 

 tion. 



(391.) The Echinorliynchi inhabit the 

 intestinal canal of various animals, to the 

 walls of which they fasten themselves by 

 a singular contrivance. In the Echino- 

 rhynchus gigas, which is found in the in- 

 testines of the hog, the head (a, fig. 74, 

 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 anchors whereby the crea- 

 ture retains itself in a position favourable 

 to the absorption of food. In fig. 74, 1, 2, 

 this aculeated proboscis is represented 

 of its natural size, relative to the body of 

 the Entozoon, as it appears 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 fig. 74, 3. "When extend- 

 ed, the position of the organ is indicated 

 by the dotted lines ; but in the drawing 

 the whole organ is represented as drawn 

 inwards and lodged in a depression formed 

 by the inversion of the iritegument, so as 

 completely to hide it within the body. 

 This inversion is produced by the contrac- 

 tion of two muscular bands, d, e, which 

 arise from the inner walls of the body, 

 and are inserted into the root of the pro- 

 Anatomy of Echinorhynchus gigas, female (after Cloquet). 1. a, proboscis ; 6, c, ovarian appa- 

 ratus ; d d, lemnisci ; e e, retractor muscles of the proboscis ; ff, alimentary tubes ; A, external 

 opening of the female generative system. 2. Anatomy of male Echinorhynchus : a, proboscis ; 

 d, lemnisci ; f, g, testes ; h, vasa deferentia, uniting together at i ; k, vesiculae seminales ; 1 1, re- 

 tractor, and n n, protruding muscles of the penis ; m, their point of insertion into o, the penis ; 

 p, generative aperture. 3. Mechanism of the proboscis : a, its extremity covered with curved 

 spines ; 6, c, its protractile sheath ; d, e, retractor muscles ; /, lemniscus; g, ovary. 



* Cloquet, Anatomic des Vers intestinaux. Paris, 1824. 



