294 



NEMATHELMINTHES. 



3, 



proboscis) (Fig. 239, R and Ms). The posterior end of this sheath 

 is fastened to the body-wall by a ligament, and by retractor muscles 

 (retinacula). 



The nervous system (Fig. 239, G) is placed at the base of the 

 proboscis, and consists of a simple ganglion formed of large cells. 

 Nerves are given off from the ganglion anteriorly 

 to the proboscis, and through the lateral retrac- 

 tors to the body-wall (Fig. 239, R). The latter 

 supply partly the muscular system of *he body, 

 and partly the genital apparatus, in which there 

 are, principally in the male animal, special 

 nerve-centres, consisting of ganglionic enlarge- 

 ments. Sense organs are entirely wanting, as 

 also are mouth, alimentary canal, and anus. 

 The nutritive juices are taken in through 

 the whole outer surface of 

 the body. In the soft 

 granular subcuticular layer 

 of the integument (epider- 

 mis}) in which, as in 

 Nematodes, cell -limits are 

 not discernible, lies a com- 

 plicated system of canals, 

 filled with a clear fluid 

 containing granules. Be- 

 neath the subcuticular layer 

 of the integument, which 

 layer is often very extensive 

 and of a yellow colour, is FIG. 240. Male of ECU 

 placed the powerful mus- 

 cular tunic; it is composed 

 of external transverse arid 

 internal longitudinal fibres, 

 which latter bound the body-cavity. The struc- 

 ture of the muscular fibres is not unlike that of 

 Nematodes. The complicated ramified system of 

 the epidermal canals, of which two principal longitudinal trunks may 

 be recognized, is filled with juices, and probably functions as a nutri- 

 tive apparatus. The epidermis and canal system of the proboscis is 

 entirely cut off from the epidermis and vessels of the trunk by a 

 thin ingrowth of cuticle. The lemnisci are two bodies which 



R 



FIG. 239. Anterior part 

 of an Echinorhynchus. 

 R Proboscis ; Rs 

 sheath of proboscis ; 

 G ganglion ; Le lem- 

 nisci : R retinacula. 



rhyncus nngnstatus (after 

 R. Leuckart). 11 pro- 

 boscis ; Rs sheath of the 

 proboscis ; Li ligament ; 

 (; ganglion ; Le lemnisci : 

 T testes ; Vd vasa defer- 

 entia ; Pr prostatic sacs ; 

 De ductus ejaculatorius ; 

 P penis; B retracted 

 bursa. 



