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AN INTRODUCTION TO ZOOLOGY 



diffusion. The nervous system is quite simple, and consists of two 

 well-marked ganglia in the head connected together by a transversely 

 placed commissure. From each of the ganglia a fine nerve cord 

 runs backwards along the lateral border of the proglottids. The 

 most conspicuous parts of the excretory system are two longitudinal 

 canals running just inside the lateral nerve through the whole 



FIG. 62. Tapeworm of the pig, Tcenia solium. 



A., entire specimen, reduced ; c.> head ; B., head or scolex, showing adhesive hooks and suckers' 

 enlarged ; C., proglottid or segment, enlarged, with mature reproductive apparatus ; ex., excretory 

 canal ; ., longitudinal nerves ; ov., ovary ; Pg., genital pore ; sh., shell gland ; ut., uterus ; i>a., 

 vagina ; vd., vas de-ferens ; vit., vitteline gland. (After Leuckart, from Parker and Haswell.) 

 From Lull. 



length of the strobilla, and therefore opening at the hinder end of the 

 last proglottid. They are connected at the posterior end of each 

 proglottid by a transverse canal, and receive a rich network of very 

 fine vessels, ramifying all through the tissues of the tapeworm and 

 terminating in branches which end blindly in highly specialised 

 cells. These cells form a pear-shaped hollow and give off a few very 

 long cilia, which hang down into the tubule and execute constant 



