PHYLUM PLATYHELMINTHES 



247 



times called the neck. The attachment of the Tape-worm to the 

 wall of the intestine is slight and temporary ; it is effected by 

 certain organs of adhesion, the hooks and suckers on the head. 



The head (Fig. 192) may be roughly described as pear-shaped, 

 but becomes four-sided at the broader end. In the middle of this 

 broader, anterior end is a rounded prominence, 

 the rostellum, round the base of which there is 

 a double row of usually about twenty-eight 

 curved and pointed chitinous hooks. The 

 rostellum is capable of being protruded and 

 retracted to a slight extent, and the position 

 of the hooks varies accordingly : when the 

 rostellum is fully retracted the points of the 

 hooks are directed forwards, and may even 

 meet in the centre ; as the rostellum is pro- 

 truded the hooks become rotated until their 

 apices come to be directed backwards. Four 

 cup-shaped suckers project slightly from the 

 surface behind the circlet of hooks. 



The body or strobila has a jointed appear- FIG. 19-2. -Head of Tsenia 

 ance, owing to its being made up of a string ^Se?TeucSirf 1 ) ified ' 

 of segments, or proglottides about 850 alto- 

 gether. These are narrower and shorter in front, gradually 

 increasing in size towards the posterior free extremity. The neck 

 or part immediately following the head is devoid of any trace 

 of segmentation. The two surfaces of the proglottides are not to 

 be distinguished by any differences visible to the unassisted eye ; 

 but that side towards which the female reproductive organs are 





o.d. 



Fig. 193. Transverse section of Teenia solium. c.m, circular layer of muscle ; ex. longitudinal 

 excretory vessel; ne. longitudinal nerve; o.d. oviduct; ov. ovary; ut. uterus. (Aftei- 

 Shipley.) 



more nearly approximated is regarded as the ventral, the opposite 

 as the dorsal surface. On one border, alternately on the right 

 and left, of each proglottis, is a little prominence, the genital 



