TAPEWORMS. CESTOIDS {Kestos, festooned). 



Flat body, in segments originating in strise in neck, rounded head, tetra- 

 gonal owing to four suckers, and often protractile proboscis and booklets. 

 Segments increase toward caudal end, becoming sexually mature and oviger- 

 ous ; longitudinal and transverse muscular fibres ; two pairs, dorsal and ven- 

 tral canals, and two nerves near borders. Each segment hermaphrodite. 

 Taenia and bothriocephalus. Stages of development : i. Mature tape-worm 

 (taenia, strobila) ; 2. Detached ripe segment {proglottis) ; 3. Ovum; 4. Six- 

 hooked-embryo (proscolex) ; 5. Larva (bladder- worm, hydatid, scolex). 

 Armed tsenise ; unarmed tsenise. Subdivisions of armed taeniae : (a) Cysto- 

 tsenia, cyst continuous with the head ; (b) Cystoidotaenia, with caudal end 

 enlarged by budding, and cyst only slightly developed. Cystotasnia are (a) 

 Cysticercus, larva with one head and cyst from one ovum ; (b) coenurus, 

 many heads in one cyst from one ovum ; (c) echinococcus, many cysts from 

 the first parent cyst, and many of these develop one head each, representing 

 a future tape- worm. Unarmed taenia. Flat-headed tape-worms : Bothrio- 

 cephala, lateral slit-like suckers in margins of head. Mostly in fish and fish- 

 eating carnivora. 



This order of worms is characterized by its flat body, made up 

 of a number of segments joined end to end and preceded by a 

 small head, rendered angular by a row of projecting suckers, and 

 often furnished with a protractile proboscis, and one or two rows 

 of booklets, by which as well as by the suckers, they attach 

 themselves to the mucosa. The segments in the narrow neck are 

 represented by simple transverse striae, which become wider apart 

 the more distant they are from the head until the segments are 

 fully developed toward the caudal end. The head is round, or more 

 usually four-sided, the suckers forming the projecting angles. 

 The body of the worm is made up of stellate anastomosing cells, 

 the whole covered by a homogeneous cuticle, in which as well as 

 in the interior, calcareous encrustations are not uncommon. Be- 

 neath the cuticle is a layer of contractile cells, then a layer of 

 longitudinal muscular fibres and finally one of transverse fibres. 

 There is no true digestive apparatus, but two pairs of canals 

 dorsal and ventral, extend back through the .successive segments 

 near their lateral borders, and open on the posterior border of the 

 terminal segment. Two lateral nervous cords run the entire 

 length of the body and are united by a transverse band at the 

 head. 



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