330 THE DEVELOPMENT OF CESTODES. 



which were perfectly developed, but others appeared only as short 

 blunt protuberances. ^ Moniez also speaks of tape-worm embryos with 

 twelve hooks. I have myself seen such cases in T. saginata and 

 F. elliptica, and Professor Eamsay-Wright has showed me, in my 

 laboratory here, embryos with ten and even twenty-four hooks. The 

 embryos are considerably larger than usual, some twice as large, and 

 they bear their hooks in groups of about six on only one-half of the 

 body. 



The statement of 0. Schmidt, lately reasserted by Kiichenmeister, 

 that the six-hooked embryos of the Tcenia dispar occurring in the 

 conimon frog are the result of an asexual reproduction ^ is quite 

 erroneous ; it is by no means difficult to demonstrate the existence of 

 their generative organs. 



The Development of Gestodes. 



G. Wagener, "Die Bntwickelung derCestoden," JVotJa ^cto^ cad. Cms. Leop.-Carol., 

 Bd. xxiv., Suppl. 1854 ; also Breslau, 1854. 



K. Leuokart, "Die Blasenbandwiirmer und ihre Enfcwickelung," Giessen, 1856, 

 Moniez, " Sur les Cysticerques," Bull. sci. dep. Nord, t. x., p. 284, 1879. 



The above account of the formation of Cestode embryos has shown 

 us that the young brood has not the least resemblance to the adult 

 forms. The young embryos (Fig. 179) are microscopic baUs, with 

 usually six apical hooks, and differ widely from the tape-worm, both 

 in shape and size. Between these two extremes we find a long series 

 of wonderful metamorphoses. 



Thirty years ago the further development of these embryos 

 was wholly unknown. Dujardin supposed that they were liberated 

 in the intestine of their host, that they passed 

 by simple metamorphosis into the so-called " head," 

 and afterwards, by forming joints, became the 

 familiar tape- worm. ^ Even v. Siebold seemed at 

 Fig 179.— Embryo of first* inclined to suppose that the six-hooked em- 

 Tcenia. (x 100.) bryos passed directly into the subsequent tape- 

 worm, and only opposed Dujardin by urging that this change could 

 hardly take place in the original habitat of the mother-animal, " since 

 the young brood was so seldom found near the Cestodes." The change 



1 Ziemssen's " Handb. d. sp. Path. u. Ther.," Art. "Darmsohmarotzer," Bd. vii., 2, p. 

 600 ; Eng. Transl., "Cyclop. Pract. Med." vol. vii., London, 1877. 



' Zeitschr. f. d. gesanvmt. Naturwiss., Bd. v., 1855. 



" Ann. Sci. nat., t. xx., p. 841, 1843 ; or, " Hist. nat. des Helminthes," pp. 545, 633, 

 1845. 



* Art. " Parasiten" in Wagner's " Handworterbuch der Physiologie," Bd. ii., p. 673, 



Brunswick, 1843. Digitized by Microsoft® 



