52 Dr. F. von Wagner on 



fission and gemmation *, that conception nevertheless could 

 well have its foundation only in the supposition that not 

 merely do fission and gemmation merge into one another 

 through unequivocal intermediate forms, but that also there 

 is justification for venturing to speak of both modes of repro- 

 duction in the general sense ; for only on such hypotheses 

 would it be permissible to extend to all cases definite results 

 of the facts found in one or more, and to elevate them into a 

 principle of general applicability. 



The conditions alluded to, however, by no means occur. 



As regards possible transitional forms, in the first place it 

 certainly appears to be beyond doubt that, especially among 

 the Cnidaria, the existence of such intermediate modes of 

 reproduction cannot be gainsaid. Yet these supposed inter- 

 mediate forms assume this aspect solely in consequence of 

 the fault}^ and indefinite character of the views which have 

 hitherto been held. Intermediate forms of this kind occur in 

 the Cnidaria just as little as in the Worms or any other 

 Metazoa. Von Koch was entirely in the right when, on the 

 basis of his minute investigation of the conditions of asexual 

 reproduction, which were, it is true, chiefly those of the 

 Palaeozoic Corals, he was induced to create a " fission-gemma- 

 tion " C' Theilungsknospung "), and included it, as well as 

 his " septal gemmation," under fission, according to custo- 

 mary views f. Yet, according to the aspects which influence 

 me, it is no less clear that, in the forms of gemmation alluded 

 to, I am bound to recognize real gemmation and not fission. 



The instances of asexual reproduction in the Worms, in 

 spite of all differences of detail, nevertheless exhibit so uni- 

 form a general character as to necessitate similar interpre- 

 tation. In contrast to these conditions the remarkable 

 gemmation of SylUs ramosa\ appears completely isolated ; as 

 yet this represents the sole case of gemmation in the Anne- 

 lids, and is probably a purely personal acquisition on the part 

 of this Syllid, which has been gained in adaptation to the 

 fundamentally altered mode of life. 



* By this I allude not merely to the connexion which is entailed by 

 the community of the same primary causes {cf. last note), but also to that 

 which would, as it were, be implied by the proof that a particular case 

 of fission could, in its origin, be traced to a particular case of gemmation, 

 or vice versa (e. g. origin of strobilation, according to Clans — ' Unter- 

 suchungen iiber die Organisation und Entwickluugder Medusen,' Leipzis-, 

 1883, p. 18).^ ' F «' 



t G. V. Koch, " Die ungeschl. Vermehrung einiger palaozoischer 

 Korallen vergleichend betraclitet," Palaoutographica, Bd. 29, p. 89. 



X " Report of the Scientific Results of the Voyage of H.M.S. ' Chal- 

 lenger,' Zoology," vol. xii. pp. 198 et sqq. 





