68 - LECTURE IV. 



as they are broad, proportions wliicli are never observed in the 

 23 Russian tapeworm. But the chief distinction between 



the Bothriocephalus latus and the Tcenia solium is 

 in the position of the generative orifices, which, in the 

 Tcenia solium, are placed near the middle of one of 

 the margins of each joint, and are generally alternate 

 {fig. 28, a, a). 



The integument of the Taenia is soft, like a mucous 

 membrane ; beneath it is a layer of delicate transverse 

 muscular fibres, and a more easily recognisable stratum 

 of longitudinal fibres. There must also be special muscles 

 for the movements and retraction of the uncinated 



Taenia solium. proboScis. 



The condition of the nervous system is a matter of analogical con- 

 jecture. Its principal part most probably exists in, or near, the 

 well-organised head, whence, as in the Trematoda, it may send back- 

 wards two delicate filaments. 



The correspondence of the digestive system with that of many 

 Distomata is more certainly known, since it consists of long and 

 slender canals continued lengthwise, with transverse connecting 

 channels in most species, through the soft parenchyme. The mode 

 of commencement of this system of canals appears to have been best 

 seen by Siebold*, who describes and figures it in the larva of a 

 tapeworm {fig. 33.), as commencing by a circular canal around the 

 opening of the fossa in which the uncinated proboscis is retracted. 

 Four longitudinal vessels are continued from this circle, which bi- 

 furcate on arriving at each of the four suckers and re-unite below 

 them, to be continued downwards as the main longitudinal vessels 

 of the body {fig. 32, I, I). These contain a clear colourless liquid, 

 and are readily seen in recent Tjeniaj subjected to moderate pressure. 

 This mode of investigation is better than that by injection, the na- 

 tural extent of which cannot be defined by distinct walls of the spaces 

 into which it may be driven. The transverse canals which connect 

 the longitudinal ones in the Tcenia solium are situated near the pos- 

 terior margin of each segment. No other system of vessels can be 

 detected in recent Taeniae scrutinised in tlie way recommended. The 

 longitudinal nutrient canals have no communication with the marginal 

 pores : they equally exist in those Cestoidea which Jiave no marginal 

 pores, and the nutriment may be received by cutaneous absorption, 

 the head being organised to serve chiefly as a hold-fast. 



The tissue of the Taeniae in which the alimentary canals are im- 



* LXIII. p. 200. pi. xiv. 



