ANNULOSA: T^NIADA. 



233 



fig. 113, "). In some of the Tceniada the scolices are called 

 " hydatids," and it is these, also, which constituted the old 

 order of the " Cystic Worms." When thus encysted within 



Fig. 114. Morphology of Taeniada. i. Ovum containing the embryo in its leathery 

 case; 2. Cysticercus longicollis; 3. "Head" of the adult Teenia solittm, enlarged, 

 showing the hooklets and cephalic suckers ; 4. A single generative joint, or pro- 

 glottis, magnified, showing the dendritic ovary (<?), the generative pore (a), and the 

 water-vascular canals (b) ; 5. A portion of a Tape-worm (strobila), snowing the 

 alternate arrangement of the generative pores. 



the tissues of an animal, the " scolex " consists simply of a 

 taenioid head, with a circlet of hooklets and four "oscula" or 

 suckers, united by a contracted neck to a vesicular body. It 

 contains no reproductive organs, or, indeed, organs of any 

 kind, and cannot attain any further stage of development, un- 

 less it be swallowed and be taken for the second time into the 

 alimentary canal of a warm-blooded vertebrate. It may in- 

 crease, and produce fresh scolices, but this takes place simply 

 by a process of gemmation. The series of changes, however, 

 whereby the scolex is converted into the " strobila," or adult 

 tape-worm, cannot be carried out unless the scolex gain access 

 to the alimentary canal of a warm-blooded vertebrate. In this 

 case, the scolex attaches itself to the mucous membrane of the 

 intestinal tube by means of its cephalic hooklets (when these 

 are present) and suckers. The caudal vesicle now drops off, and 

 the scolex is thus converted into the "head" of the tape-worm. 

 Gemmation then commences from its posterior extremity, the 

 first segments being immature. As the first -formed joints, 

 however, are pushed further from the head by the constant 



