CESTODA. 



245 



terminal swelling by which it at- 

 taches itself. This anterior swollen 

 pp.rt is distinguished as the head of 

 the tape-worm, but it is mainly its 

 external form which entitles it to 

 this name. In CaryopTiyllaeus the 

 head armature is very weak, and 

 consists of a lobed fringed expan- 

 sion. The apex of the head often 

 ends in a conical projection, the 



FIG. 196ff. Head of Tacnia soli um, 

 viewed from the front (apical surface), 

 with rostellutn and double circle of 

 hooks. The four suckers are visible 

 (from Glaus). 



rostellum, which is armed with a 

 circle of hooks, while the lateral 

 surfaces of the head are furnished 

 with four suckers (Taenia, Fig. 

 196). In other cases only two 

 suckers are present (Botlirioceph- 

 alus) ; or we find suckers of more 

 complicated structure and beset with 

 hooks (Acanthobofhriurri), or four 

 protrusible proboscises beset with 

 recurved hooks (Tetrarhynchus, Fig. 

 198) ; while in other genera the 

 head armature presents various 

 special forms. 



That portion of the animal, which 

 follows the head and is distin- 

 guished as the neck, shows, as a 

 rule, the first traces of commencing 

 segmentation. The rings, which are 

 at first faintly marked and very 

 narrow, become more and more 

 distinct and gradually larger the 

 further they are removed from the 

 head. At the posterior extremity 

 the segments or proglottides are 

 largest, and have the power of 

 becoming detached. 



FIG. 197. Taenia saginata (mediocanel- 

 lata), natural size (after R. Leuckart). 



