332 THE DEVELOPMENT OF CESTODES. 



and extended both by Kiichenmeister^ and by v. Siebold'' and his 

 school. 



After these experiments it could no longer be doubted that the 

 bladder-worms stood in definite genetic relations with tape-worms, 

 and particularly with Tcenice. 



In order to appreciate the full import of this discovery, we must 

 remember that since the time of Zeder and Eudolphi the cystic worms 

 were commonly regarded as representatives of a special group of Hel- 

 minths — the Cystici. It was of course known that these bladder- 

 worms exactly resembled Tcenice in the formation of their head, but 

 the presence of a water-bladder, instead of a ribbon-like jointed body, 

 was considered distinctive. It was this same characteristic which had 

 concealed the true, or even the animal, nature of these organisms till 

 towards the end of the seventeenth century, when the researches of 

 Hartmann, Tyson, and Malpighi showed that it was no longer possible 

 to regard them as simple hydatids.^ Their occurrence in parenchy- 

 matous organs seemed also a sufficient reason for separating them from 

 the tape-worms, to which they had been already referred by Pallas 

 and Goze.* As to the absence of sexual organs in these cystic worms, 

 that was hardly a difficulty. The calcareous bodies (p. 281) were in 

 fact often regarded as eggs, and when the true state of the case was 

 noticed, it was only another proof of the generatio cequivoca. 



The result of Kiichenmeister's experiments, though new, and sur- 

 prising to the majority of physicians and zoologists, was yet not 

 altogether unforeseen. Dujardin and v. Siebold had already advanced 

 the supposition that the bladder-worms were not independent animals, 

 but only developmental stages of Tcenice.^ Both supposed that the 

 cystic worms were developed out of tape-worm germs which had reached 

 the body-parenchyma, instead of only the alimentary canal of their 

 host, and had, in consequence of the unwonted environment, become 

 abnormally modified. Von Siebold especially supported this theory 

 of the degeneration of tape- worms into bladder-worms.^ The tape- 



1 " XJeber die TJmwandlung d. Finneu in Tsenien," Prager Vierteljahrsschr., 1852. 



' " Ueber die Verwandlung dea Cystioercus pisiformis in Taenia serrata," Zeitschr.f. 

 wiss. Zool., Bd. iv., p. 400, 1852 ; and as to the metamorphosis of Echinococcus-hTOod. into 

 Tmnice, ibid., p. 409. (Lewald, " De cyatioeroorum in tienias metamorphoai," Dissert, 

 inaug. Wratislav, 1852.) 



" See, in greater detail, Leuokart, loc. cit., pp. 1-27, &o. 



* In hia group of tape-worms Goze distinguislied the Tcsnice intestirudes inhabiting 

 the intestine, and the Tcmice viscerales occurring elsewhere. Others united the cystic 

 worms to the other Tceniw under the title Tcenice vesiculares. 



° In the second edition of his work (" Paraaiten," p. 60, note), Zuohenmeister 

 underrates v. Siebold's share in the solution of the problem in a way which is, to every 

 unprejudiced critic, utterly unfair, and he accompanies it with the unparalleled assertion 

 (p. 163, note) that " no one has so grievously offended in the study of the Cestodes" as the 



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