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MANUAL OF ZOOLOGY 



many times, often hundreds of times, the greatest breadth, 

 so that the animal assumes the form of a long, narrow ribbon 

 or tape. This ribbon is not continuous, but is made up of 

 a string of segments or proglottides. Towards one end the 

 body becomes narrower, terminating in a rounded knob — 

 the head or scolex. On the head (Fig. 75) is a circlet 

 of hooks borne on a rounded prominence, the rostellum, 

 which is capable of being protruded and retracted to a 

 certain extent ; at the sides are four suckers. By means of 

 these hooks and suckers the head is 

 attached to the wall of the intestine 

 of the host, the elongated body lying 

 free in its interior. The part of the 

 body just behind the head {neck) is 

 not divided into segments. The most 

 anterior segments are much shorter than 

 those further back, and not so distinctly 

 separated off from one another. The 

 surface is devoid of cilia, as in the 

 Trematodes. A digestive cavity is, as 

 already stated, absent ; but there is a 

 distinct nervous system, and a system 

 ofTaenia of water-vessels with flame-cells. In the 

 posterior region of the body each pro- 

 glottis (Fig. 76) is found to contain a 

 complete set of hermaphrodite reproductive organs similar 

 in general plan to those of the liver-fluke. The ova, when 

 fertilised, are enclosed in a chitinoid shell, and received 

 into a uterus. In the most posterior segments the uterus 

 is a large branched tube distended with enormous quantities 

 of these eggs, and the other parts of the reproductive appa- 

 ratus have become absorbed. These "ripe" proglottides, 

 as they are termed, drop off, one by one, from the pos- 



FiG. 75.— He 



solium, magnified. 

 (After Leuckart.) 



