MANUAL OF ZOOLOGY 



SECT. 



FIG. 69. Head of Taenia 

 SOlium, magnified. 

 (After Leuckart.) 



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 of water-vessels with flame- 

 cells. In the posterior region of the 

 body each proglottis (Fig. 70) is found to contain a com- 

 plete 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 quan- 

 tities of these eggs, and the other parts of the reproductive 

 apparatus have become absorbed. These " ripe " pro- 

 glottides, as they are termed, drop off, one by one, from the 

 posterior end, and reach the exterior with the faeces of the 

 host. At the same time new proglottides are constantly 

 being formed by the appearance of new ring-like grooves 

 behind the neck region. This dropping off of ripe 

 proglottides from the posterior end, and the formation of new 

 ones behind the neck, results in a gradual shifting back- 

 wards of the proglottides. As each proglottis passes back- 



