PHYLUM PLATYHELMINTHES 



I6 5 



.---' sc 



{vas.de}.). Eggs arise in the bilobed ovary {ov) and pass into 

 a tube, the oviduct. Yolk from the yolk-gland (gl.vit) enters 

 the oviduct and surrounds the eggs. A chitinous shell is then 

 provided by the shell gland (schld) and the eggs pass into the 

 uterus {titer). The eggs have in the meantime been fertilized 

 by spermatozoa, which probably come from the same proglottis, 

 and move down the vagina (vag). As the proglottides grow 

 older the uterus becomes distended with eggs and sends off 

 branches (Fig. 107,*), while the rest of the reproductive organs 

 are absorbed. The ripe proglottides break off and pass out of 

 the host with the faeces. 



The eggs of Tamia solium develop into six-hooked 'embryos 

 (Fig. 109, a) while still within the pro- 

 glottis. If they are then eaten by a pig, 

 they escape from their envelopes (Fig. 

 109, b) and bore their way through the 

 walls of the alimentary canal into the 

 voluntary muscles, where they form cysts 

 (Fig. 109, c). A head is developed from 

 the cyst wall (Fig. 109, d) and then 

 becomes everted (e). The larva is known 

 as a bladder-worm or cysticercus at this 

 stage. If insufficiently cooked pork con- 

 taining cysticerci is eaten by man, the 

 bladder is thrown off, the head becomes 

 fastened to the wall of the intestine, and 

 a series of proglottides is developed. 



b. Cestoda in General 



Fig. 1 10. — A uniseg- 

 mentalcestod, Archigetes 

 sieboldii, from the coelom 

 of a worm, Tubifex 

 rivulorum. app, persist- 

 ent larval appendage; 



The Cestoda are all ento parasitic flat 



worms, called tapeworms ; they inhabit go, genital pore; hk, per 



the alimentary canal of vertebrates in the ^%^f c> Srj 



adult stage. The body consists of a head te, testes; yg, yolk- 



or « scolex » followed by a chain of similar g"^ £ t u ? al g° 



joints or " proglottides " which are budded tory, after Leuckart.) 



