434 GROWTH AND STRUCTURE OF T.ENIA SAGINATA. 



they were always directed forwards, so that the muscular mass of the 

 sucker thus came to lie behind the openings, embedded in the paren- 

 chyma of the head, whose form was essentially determined by this 

 circumstance. 



Histologically the suckers only differ from the ordinary type in 

 the special strength of their musculature. The walls have an unusual 

 thickness, and are so firmly united that they can be separated from 

 their surroundings by even gentle pressure. 



But the size and strong development of the suckers are not the 

 only distinctive features in the structure of the head. The absence of 

 the circlet of hooks is not less noteworthy, and determines the re- 

 markable flattening of the apex, which is in such contrast to allied 

 forms; the apical surface of the worm being in no case, however, 

 perfectly level. 



Even Batsch mentions in his Tcenia dentata a " media papilla " of 

 small size lying between the suckers. Similarly, Bremser x saw at 

 this point " an arched protuberance on which one always notices a 

 circle with a small, hardly perceptible, opening in its centre." He 

 regards this circle as rostellum, as may be inferred from the further 

 observation, that it " often, but not always " (that is in Tcenia solium, 

 but not in T. saginata), bears a double circle of hooks. 



I have since shown the truth of this identification. 3 T. saginata 

 does indeed possess a rostellum, as has been amply confirmed both by 

 Nitsche and Moniez. 3 The rostellum is, however, but a small one 

 (0'2o mm.), though essentially agreeing with that of related forms. It 

 consists of a well-defined lenticular body, mainly composed of fibres, 

 which are stretched straight between the two opposite surfaces. They 

 have thus a longitudinal course, and are crossed posteriorly by a 

 system of radial fibres. The muscles which usually run along the 

 under part of the rostellum are only slightly differentiated, and 

 are hardly recognisable as distinct structures, though in arrangement 

 and course they certainly resemble those of allied forms. 



So far, then, the rostellum of Tcenia saginata, in spite of its 

 comparatively weak development, possesses essentially the structure 

 seen in the hook-bearing cystic tape-worms. But, while in the 

 latter the rostellum is covered by a prominent layer of parenchyma 



1 Loc. cit., p. 100. Bremser refers there to his figure (Tab. in., Fig. 3). This is to be 

 referred to T. saginata and not to T. solium, as Kiichenineister would have it (" Parasiten," 

 2d ed., p. 153, note). It was taken from a living hookless specimen by Bremser in 

 Vienna. 



2 First German edition of this work, Bd. i, p. 409. 



8 Kiichenmeister says that this structure has been "first accurately described by 

 Landois and Sommer," but he forgets to say where. In the well-known paper on T. 

 mediocanellata it is not mentioned at all. 



