ACANTHOCEPHALA. 



295 



project through the muscular tunic into the body-cavity at the base 

 of the proboscis (Fig. 240, Le). They consist of epidermis, 

 continuous with that of the proboscis, and a thin muscular coat, 

 and they contain a great number of anastomosing canals, It has 

 been suggested that the epidermal spaces of the lemnisci and 

 proboscis are organs for the protrusion of the 

 proboscis ; the fluid which in the retraction of 

 the proboscis enters the epidermal spaces of 

 the lemnisci being by the contraction of these 

 latter organs forced back into the walls of the 

 proboscis, so bringing about its protrusion. 

 According to Schneider, the vessels of the 

 lemnisci open into a circular vessel in the 

 integument, and only communicate with the net- 

 work of canals in the proboscis, while the other 

 dermal vessels (nutritive apparatus), the con- 

 tents of which differs from that of the vessels 

 of the lemnisci, are, as above stated, completely 

 shut off from the latter. 



It has recently* been asserted that there is in Echino- 

 rhynchus gigas a pair of nephridia. They consist of a 

 bunch of tine tubes, which terminate in a sieve-plate, 

 the pores of which open into the body -cavity. The 

 sieve-plate carries on its inner side a bunch of flagella. 

 The fine tubes unite to form a duct, which joins its 

 fellow. The single duct so formed opens into the 

 generative duct. 



Generative organs. The body-cavity through 

 which fluids circulate encloses the greatly- 

 developed generative organs, which are attached 

 to the end of the sheath of the proboscis by the 

 ligament (Figs. 240* and 241 1). The sexes are 

 separate. The male (Fig. 240) has two testes 

 (T\ and the same number of efferent ducts 

 ( Vd). The latter unite behind to form a ductus 

 ejaculatorius (De), which is often furnished 

 with six or eight glandular sacs (Pr), and a conical penis (P), at the 

 bottom of a bell-shaped protrusible bursa (B), situated at the posterior 

 end of the body (Fig. 240). The generative organs of the larger 

 females (Fig. 241) consist of the ovary developed in the ligament; of 



* J. E. Kaiser "Die Acanthocephalen u. ilire Entwick." Bill. Zool. Bd. 2, 

 Heft 7, 2 Theile, 1892. 



FIG. 241. Generative 

 ducts of a female 

 Echinorhynchus tricho- 

 cephahis from the so- 

 called dorsal side, i.e., 

 the side of the pos- 

 terior opening of the 

 bell. The opening of 

 the uterine bell b 

 looking forward and 

 its relation to the liga- 

 ment I. c posterior 

 opening of the bell, by 

 which the unripe eggs 

 pass back into the 

 body-cavity; d uterus; 

 e vagina (after Kaiser). 



