308 



ZOOLOGY 



SECT. 



>- l ff 



In correspondence with the absence of mouth and anus there is no trace of 

 enteric canal, the Acanthocephala resembling in this respect the Cestoda, the 

 only other class of Metazoa which is entirely anen- 

 terous. Food is thus, as in tapeworms, taken 

 entirely by absorption by the general surface of the 

 body. 



The proximal end of the proboscis is contained 

 in a muscular sheath sunk in the anterior end of 

 the trunk, and is provided with four retractor 

 muscles (Fig. 254, r.m.). The muscles of the sheath 

 are circular and act as protractors. At the sides of 

 the base of the proboscis two club-shaped organs, 

 the lemnisci (lm.), hang down into the body-cavity. 

 Their function is quite unknown, but they have 

 been compared with 

 the cervical glands of 

 certain Nematodes (p. 

 301). 



In the body-wall 

 run two longitudinal 

 vessels (v.) containing 

 a granular fluid, and 

 connected with a net- 

 work of fine canals in 

 the proboscis, bursa, 

 etc. The function of 

 these vessels is not 

 known with certainty : 

 they may have to do 

 with the absorption 

 and circulation of 

 nourishment. 



The central ner- 

 vous system (Fig. 

 255, nv.) is represented 

 by a single large gang- 

 lion placed at the base 

 of the proboscis, and 

 sending off nerves in 

 various directions. In 

 the male there are 

 also two ganglia sup- 

 plying the reproduc- 

 tive organs. Organs 

 of sense are wholly 

 absent. 



A pair of remark- 

 able excretory orgrans 

 or nephridia (Fig. 257) 

 have been found to 

 occur in Echino- 

 rhynchus gigas. These 

 consist of a pair of 

 ramified protoplasmic 

 masses situated in the 

 body-cavity at the posterior end, near the genital aperture. In the interior 

 is a system of branching canals, the terminal branches of which, each contained 

 in one of the terminal lobes of the tree-like nephridium, are provided with 



Fid. 255. Echinorhynclius 

 gigas. Dissection of male. 



b. bursa ; c. gl. cement glands ; Fra. 256. Echinorhynclius 



lm. lemnisci ; nv. nerve- gigas. Dissection of female 



ganglion ; pr. proboscis ; s. Ig. (semi-diagrammatic), b. bell ; 



suspensory ligament; ts. testis; lm, lemnisci; pr. proboscis; 



?'. df. vas deferens. (After s. ovtj. swimming ovaries ; ut. 



Leuckart.) uterus ; vg. vagina. 



