FREE JOINTS, OE PROGLOTTIDES. 41 



"V 



Proglottides takes place at the posterior end of the scolex by 

 asexual reproduction; viz., by a simple process of growth and 

 division. If we compare this process with the phenomena of 

 the Alternation of Generations, we shall discover in it all the 

 essential characters of the latter. The matured joints, or the 

 sexual individuals, of the Cestoidea in their proglottis form, pro- 

 duce a brood of embryos armed with six booklets, which are 

 quite dissimilar in shape from their parents, the Proglottides, and 

 remain so, since at a later period they assume the scolex form, 

 and take on the functions of an agamozooid. From the posterior 

 end of the body of such a scoliciform agamozooid a series of joints 

 are developed ; that is to say, a generation of sexual individuals, 

 which again present the original proglottis form. In their 

 organization, the Proglottides , apart from their sexual apparatus, 

 so far resemble the scolices, from which they have been pro- 

 duced, that they possess no oral aperture, and moreover are 

 subject to a deposit under their integument, of those glassy cal- 

 careous particles which I have already mentioned. 



It seems, at first, paradoxical to say that the joints of a tape- 

 worm, which have hitherto been believed to be mere parts of one 

 animal, should be considered as individuals; but whoever will 

 observe, with an unprejudiced eye, a fully developed Tcenia with 

 its sexually matured joints, must be convinced that it is no 

 simple animal, but one composed of many individuals. The 

 joints of a Tcenia , when quite mature, become detached from one 

 another with the greatest ease ; the separated joints for a long 

 while preserve their form and remain quite fresh and lively, 

 being even capable of locomotion, and always seeking to dis- 

 burden themselves of their eggs before dying. Even the older 

 naturalists had regarded the single, separate joints of a Tcenia as 

 separate individuals, whilst others again, described the joints of 

 the common tape- worm of Man, (Tcenia to/stem), as " Vermes 

 cucurbitini" Later helminthologists, however, rejected the idea 

 that a Tcenia was composed of " Vermes cucurbitini" and especially 

 objected 1 to the view of Vallisnieri and Coulet, 2 who maintained 

 that the Tcenice were produced by the mutual adherence of a 

 number of the cucurbitine worms into a complex, jointed whole. 



1 See his ' Considerazioni ed Esperienze intorno alia Generazione de' Verrai del Corpo 

 umano.' Padooa, 1710, p. 63. 



8 ' Tractatus de Ascaridibus et Lumbrico lato.' Lugduni Batavorum, 1729, pp. 37, 

 56, &c. 



