34 Dr. F. von Wagner on 



same degree in the outward manifestation of the fission, until 

 at last it assumes the position of a more secondary final act. 



There is a natural inclination on the part of the observer 

 of this class of fission to regard the extensive reconstructions 

 as the essence of the process, while considering as of trifling 

 moment the uninteresting separation. 



It is, however, other things being equal, not so mucli the 

 extent as the nature of the regenerations which causes many 

 cases of fission to be interpreted as gemmation. Thus gem- 

 mation is especially discovered in all kinds of worms, whereas, 

 so far as my own conviction goes, in these animals, with 

 perhaps the sole exception of the remarkable reproduction of 

 SyUis ramosa, with which M'Intosh has made us acquainted*, 

 fission alone occurs. 



For, on observing the course of the regenerations, manifold 

 features are seen, which are found in the formation of a 

 number of organs in the ontogeny of many animals, and 

 which we are wont to term in ordinary phraseology "sprouts" 

 or " buds." Of the extent to which this outward similarity 

 of what are at the bottom very different processes is taken as 

 internal homiOgeneity, owing to the consonance of their 

 designations, the Naids are a classic example. The gemma- 

 tion which is alleged to exist among these worms reduces 

 itself to the appearance of so-called " zones of gemmation " 

 in their asexual reproduction. Herein it must remain unde- 

 cided whether this multiplication is to be regarded as 

 " gemmation," because " zones of gemmation " are formed, 

 or whether, on the contrary, these latter receive their desig- 

 nation because the whole process is to be taken as an instance 

 of gemmation. The " zones of gemmation " of the Naids 

 are, however, nothing more than zones of regeneration, 

 within which proceeds the development of organs and parts 

 of organs, which is necessarily combined with paratomy. 

 That the latter is an actual new formation is in accordance 

 with the nature of the case ; it is related to the fission of the 

 Naid in precisely the same way as is the formation of peri- 

 stome and pharynx to the reproduction of Stentor. If, there- 

 fore, we speak of such processes as fission depending upon 

 " gemmation " or " processes of gemmation " j, we do not 

 use the expression " gemmation " in the sense of the mode of 



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

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



t Thus, according to Vogt and Tung, the asexual reproduction of 

 Microstoma consists " of repeated transverse fissions, and proceeds from 

 axial hudding at the posterior end " (C. Vogt and E. Yung, ' Lehrbuch 

 der praktischen vergl. Anatomie,' i. p. 284, Braunschweig, 1888). 



