CESTODA. 781 



removed and the liead left behind, the worm will be again re- 

 produced. 



The head or scolex, in addition to its power of continually 

 budding off chains of segments, is provided with organs by- 

 means of which it fastens itself to the wall of the alimentary 

 canal. These organs of attachment in the Bothriocephalus take 

 the form of two longitudinal gi'ooves, hence the name, while 

 in the Tcenia the sides of the head are provided with four 

 sucking discs. In addition to the four suckers, some tape-worms 

 {Tcenice armatce) have circles of hooks anterior to the suckers, 

 each hook formed in a little pocket. These hooks have sharp 

 projecting points, which serve as anchors for the tape-worm. 

 Their presence or absence, their size, form, and number, are 

 often very characteristic, and their examination is often facili- 

 tated by the use of caustic potash, in which the hard chitinous 

 material of which they are composed is insoluble. 



Following the head come the youngest segments, as yet narrow 

 and short, and not plainly distinguishable from one another, 

 often spoken of as the ncch. Proceeding backwards from the 

 nccTc, the segments become broader and longer, and more distinct 

 from one another. The hindmost segments have reached the 

 full size, are capable of separating from the others, and can even 

 have an independent existence for a time. Ultimately these 

 detached segments wander out of the body, or are expelled with 

 the fseces, when they die and decay ; but the ripe eggs provided 

 with their hard shells retain their vitality, and are ready, under 

 favourable conditions, to undergo a series of metamorphoses, 

 whose final term is the adult tape- worm. 



Each segment is provided with a complete set of male and 

 female reproductive organs, so that, if we take into account the 

 fact that the segments can detach and lead for a time an in- 

 dependent existence, we may regard each segment or proglottis as 

 a complete hermaphrodite individual. In the youngest segments 

 the sexual organs are not yet developed, but in the half-ripe 

 segments the male and female organs are distinguishable, whereas 

 in the completely ripe segments the uterus loaded with its eggs 

 is the conspicuous part. The form of the uterus of the ripe 

 segment is very characteristic, and may be readily observed by 

 pressing the ripe segments between two slips of glass, and ex- 

 amining with the naked eye or a pocket lens. For example, in 



