J28 CESTODES. PHYLUM PLAT YHELMINTHES 



is no excuse for the illiterate form, proglottid) is pushed away 

 from the neck as the next is formed, so that a cham is produced 

 with the youngest links most anterior. Such a cham is called a 

 strobila The proglottides thus differ in their formation and 



Fig. 91. — The life-history of Tcsnia solium. — After Leuckart. 

 I. Six-hooked embryo in egg-case ; 2. proscolex or bladder-worm stage, with invaginated head ; 3. bladder- 

 worm with evaginated head ; 4. enlarged head of adult showing suckers and hooks ; 5. general view 

 of the tapeworm, from small head and thin neck to the ripe joints ; 6. a ripe joint or proglottis with 

 branched uterus ; all other organs are now lost. 



arrangement from the segments of annelids, anthropods or 

 chordates. When a proglottis is formed it possesses nervous tissue 

 and execretory canals continuous with those of the head ; as it 

 grows older it becomes larger, and reproductive organs develop 

 in it. Young proglottides are broader than they are long, but these 

 proportions are reversed in those which are sexually mature. 



The body is covered with a cuticle, under which lies a la^^er of 

 circular muscle fibres and then one of very deep epidermal cells 



