CESTODA 



75 



apparatus of four suckers and a circlet of hooks (Fig. 39), which 

 are borne by the "head" or "scolex," being that part of the 

 worm which is directly 

 derived from part of the 

 larva, and which contains 

 the central, commissural 

 portion of the nervous 

 system. Firm adhesion 

 to the host's intestine is 

 necessary, in order to avoid 

 the loosening action of the 

 peristaltic movements of 

 the intestine as the food 

 passes along. The heads 

 of different Cestodes ex- 

 hibit a marvellous variety 

 of suckers and hooks, from 

 a mere muscular depres- 

 sion in Schistocephalus, to 

 the compound proboscides 

 of Tetrarhynchus l which 

 is found in Elasmobranchs. 

 The jointed body, often 

 of enormous length (up 

 to 20 yards in Bothrio- 

 cephalus latus), is usually 

 Separated from the head Fl - ^-Cattiobothriumaffine^ from the in- 

 testine qf Torpedo, x 43. hd, Head ; Me, 



by a Slender neck, from hooks ; hi, lobes of the head ; ov, ovary ; pe, 

 whioh thp -nrnrrlnf-Hrlp* arp P enis ' P** penis-sheath ; te, testes ; ut, uterus ; 

 Wfticn tne proglOttldeS are ^ vag i na 7^ )yo lk-glands. (After Pintner.*) 



segmented off from behind 



forwards, and become more and more individualised as they 

 recede farther away from the neck by the intercalation of 

 younger joints. Thus in Fig. 36 the mature, distal proglottis 

 has passed through all the stages represented by the other 

 segments. The longitudinal muscles, the nerves, and excretory 

 vessels which supply the proglottides are continuous throughout 



1 For figures of various scolices see van Beneden, Mimoirc sur les vers Intestin- 

 aux, 1861 ; Braun in Bronn's Thierreich, Cestoda (in progress), Bd. iv. PI. 

 xxxviii.-xlv. 



2 Arbeit. Inst. Wien, iii. 1881, p. 163 ; see also ibid, i: . 1890, p. 57. 



