692 THE ANATOMY OF BOTHRIOCEPHALUS LATUS. 



and development of the yolk-glands, peculiarities are to be observed 

 which never occur in the Tcenice, and which prove this tape-worm to 

 belong to a markedly divergent group of Cestodes. The same charac- 

 teristic distinctions obtain, with more or less uniformity, in the 

 related species of Bothriocephalus, and especially in the larger forms 

 which are found in mammals. 1 



We have already outlined the steps in the historic growth of our 

 knowledge of these peculiarities, nor shall we do more than recall 

 that it was not the nearly related parasites which supplied the basis 

 for the distinction and definition of the species under discussion, but 

 the large-jointed Tcenice of man. 



The Genital Apertures and their surroundings will first occupy us 

 in describing the reproductive system in detail 



A first glance at a ripe adult joint seems only to reveal two 

 genital apertures. Situated one behind the other, separated by a 

 short distance (0'3-0*4 mm.), varying slightly with the state of 

 contraction, these apertures lie in the middle region of the ventral 

 surface, somewhat approximated to the anterior margin of the joints. 

 They are usually found, as Eschricht reports, on the posterior limit 

 of the first quarter of the joint, yet cases may be observed where 

 they have been displaced by the state of contraction, either further 

 forwards or backwards. Even Linnd observed these two openings, 

 but thought erroneously that they occurred only in certain specimens 

 (his Tcenia vulgaris), and that in others (T. lata) only a single 

 aperture was present. 



The anterior opening is seen on closer examination to be the male. 

 It is larger than the one behind, and forms usually a gaping trans- 

 verse cleft, from 0'25 to 0*34 mm. broad, the upper lip of which is 

 protruded outwards by the cirrhus-pouch which lies above it. The 

 penis is sometimes seen projecting as a small filamentous appendage. 

 The second, also transverse, aperture, which serves for the exit of the 

 ova, is scarcely half as broad as the upper, but is also somewhat 

 raised, so that the whole area surrounding the genital apertures 

 almost always protrudes in the form of a slight elevation. In fresh 

 specimens this protruding area is readily recognisable through its 

 whitish colour, which is due, not wholly and exclusively to the 

 subjacent tissue, but also to numerous small papillse, which occupy 



1 See on these forms Krabbe, " Recherches helminthologiques en Danemark et en 

 Islande," Copenhagen, 1866, pp. 27-39. The various species are somewhat difficult to 

 distinguish, but I think T am warranted, on the strength of repeated investigations, in 

 affirming that in the organization of the reproductive system, and especially in the 

 structure of the uterus, in the character of the papillary area, and in the disposition of 

 the yolk-glands, differences obtain among them not less than those which distinguish the 

 large -jointed Tcemce. 



