48 Dr. F. von WaQ:ner on 



t)' 



Very recently tlic customary views upon fission and gem- 

 mation, wiiich conform more or less to Hasckel's statements, 

 have also been criticized and rejected by von Kennel, vvho in 

 so doing arrives at the conclusion " that neither equality or 

 inequality of the products of division, nor difference or agree- 

 ment of age, nor even the possibility of distinguishing 

 between the original and the new individual, furnish us with 

 the means of separating fission and gemmation " *. 



It appears to me to be superfluous to add anything further 

 to the critical statements of Goette and von Kennel, with the 

 results of which I am in accord. As regards Goette's defini- 

 tions of fission and gemmation which are quoted above, they 

 confine themselves too strictly to conditions which are of 

 importance for the special question of the interpretation of 

 strobilation to suffice for a more general application. I there- 

 fore turn to the definitions of the conception of fission and 

 gemmation which have lately been developed in comprehen- 

 sive fashion by von Kennel. 



"]f we compare all reproductive processes with one 

 another," says von Kennel, " we find that in one group the 

 mass of the products proceeding from the reproduction, when 

 taken together, is equal to the mass of the original individual 

 before the commencement of the visible changes by which 

 the process was ushered in. In all other cases reproduction 

 is introduced by the appearance of new portions, which have 

 nothing to do with the individual, through an accession of 

 organized substance, so that the sections, after becoming 

 independent, represent in their entirety more mass than was 

 possessed by the original animal before the appearance of 

 the reproductive phenomena. We may term the former class 

 fission, the latter gemmation " f- 



It follows from this that von Kennel regards the presence 

 or absence of growth as the sole criterion of gemmation or 

 fission respectively. That in the case of the latter at any 

 rate von Kennel's definition betokens an artificial and arbi- 

 trary limitation is manifest without further comment. 



But if we follow out von Kennel's assertions to their 

 logical conclusion we arrive at the result that no instances 

 whatever of fission occur within the limits of the Metazoa. 

 For it is impossible to mention any case of asexual reproduc- 

 tion in these animals in wMcli " the mass of the products 

 proceeding from the reproduction when taken together is equal 



* J. V. KeDiiel, 'Ueber llieilung und Knospung- der Thieie/ Dorpat, 

 1888, p. 14. 



t J. V. Kenuel, oj), cit. pp. 14 et sqq. 



