294 



NEMATHELMINTHES. 



proboscis) (Fig. 239, R and Rs). 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 the 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 



FIG. 239. Anterior part and of a yellow Colour, is FIG. 240. Male of EcMno- 

 of an EcJiinorhijncJius i j_i r i rhyncus QfliQustCLtus (after 



R Proboscis;"^ P laced the Powerful niUS- R / Leuc J rt) . ^ pro . 



sheath of proboscis ; Clllai tllllic ; it is Composed boscis ; Rs sheath of the 



of external transverse and 

 internal longitudinal fibres, 



G ganglion ; Le lem- 

 nisci ; R retinacula. 



proboscis ; Li ligament; 

 G ganglion ; Le lemnisci ; 

 T testes ; I'd vasa defer- 

 entia ; Pi- prostatic sacs ; 



which latter bound the body-cavity. I he struc- De ductus ejacuiatorius ; 

 ture of the muscular fibres is not unlike that of p P enis : B retracted 



bursa. 



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 



