ENTOZOA. 49 



sibly longer, narrower anteriorly, thicker and broader at the pos- 

 terior margin, which slightly overlaps the succeeding joint. The 

 last series of segments are sometimes twice or three times as long 

 as they are broad, proportions which are never ob-, 

 served in the Russian tapeworm. But the chief dis- 

 tinction between the Bothriocephalus lattis and the 

 TcBiiia solium is in the position of the generative orifices ; 

 which, in the Tccnia solium, are placed near the middle 

 of one of the margins of each joint, and are generally 

 alternate {fig. 22, a, a). 



The integument of the Tsenia is soft, like a mucous 

 membrane ; beneath it is a layer of delicate transverse 

 jii^J muscular fibres, and a more easily recognisable stratum 

 of longitudinal fibres. 



Taenia soliuni. ° 



The condition of the nervous system is a matter 

 of analogical conjecture. Its principal part, no doubt, exists in, or 

 near, the well-organised head ; where, as in the Trematoda, it may 

 form a ring round the gullet, and send backwards two delicate fila- 

 ments. The correspondence of the digestive system with that of many 

 Distomata. may be stated with certainty. The alimentary tube, com- 

 mencing at the minute central mouth, soon bifurcates; and each di- 

 vision is continued as a slender unvarying canal throughout the 

 whole length of the worm, near the margin of the segments : the 

 two longitudinal canals are connected together by transverse canals, 

 one of which is situated at the posterior margin of each segment. 

 The longitudinal nutrient canals have no communication with the 

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

 marginal pores. 



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

 bedded, is beset with numerous minute nucleated cells. These doubt- 

 less take an important share by their assimilative and reproductive 

 powers in the general nutrition of the body. 



The Taenias are androgynous, and each joint contains a compli- 

 cated male and female apparatus equal to the production of thousands 

 of impregnated ova. The ova are developed in a large, branched 

 ovarium {fig. ^2, c), occupying almost the whole space included by the 

 nutrient canals, at least in the posterior segments, where it is very con- 

 spicuous from the amber colour of the more mature ova. The oviduct 

 is continued from near the middle of the dendritic ovary to the mar- 

 ginal papilla, where it terminates by a small orifice posterior to that of 

 the male organs. The parts of the male apparatus which have at pre- 

 sent been recognised, consist of a small pyriform vesicle {fig. 22, b), 

 situated near the middle of the posterior margin of the segment ; this, 



E 



