MANUAL OF ELEMENTARY ZOOLOGY 



proglottides. The life-history of Tama solium may be 

 summed up as follows : — 



.Egg->Onchosphere->Cysticercus-*Scolex-» Adult. 



It will be seen that only one generation is involved, 

 unless each proglottis be regarded as a complete individual, 



1 ! ? 3 4 



WSM 



mm®,?. 



Fig. 131. — A transverse section through a proglottis of Tania in which 

 the reproductive organs are well developed. — From Shipley and 

 MacBride. 



r, Cuticle ; 2, long-necked cells of ectoderm ; 3, longitudinal muscle fibres cut 

 across ; 4, layer of circular muscles ; 5, split in the parenchyma which lodges a 

 calcareous corpuscle ; 6, ovary; 7, testis with masses of male germ-mother-cells 

 forming spermatozoa ; 8, longitudinal excretory canal ; 9, longitudinal nerve 

 cord ; 10, uterus ; it, oviduct. 



and not merely as a part of the parent body broken off to 

 carry the eggs. 



Other common tapeworms are : Tania saginata, without 



hooks, found in man, with the bladder-worm stage 

 Tapeworms m tne ox > ■^ ser *' ata m tne dog, with a bladder- 



worm in rabbits, hares, and mice ; T. cmnurus in 

 the dog, with the bladder-worm known as Ccenurus cere- 

 bralis in the brain of sheep and other hoofed animals, where 

 it causes " staggers " ; and T. echinococcus in the dog, with 

 the bladder-worm Echinococcus in sheep, oxen, pigs, and 

 sometimes in man. The latter two species produce in the 

 bladder-worm stage numerous heads. Since only one of 

 these can be regarded as continuing the individuality of the 

 bladder-worm, the others must be looked upon as buds from 

 it, so that there is here a metagenesis. 



The harm which tapeworms do by robbing their host of 

 food is generally insignificant. Their action in setting up 



