Fission and Gemmation in the Animal Kingdom. 29 



also a starting-point would be gained in the Animal Kingdom 

 itself from which we could criticize other methods of propaga- 

 tion ; for we should still have to separate the material in them 

 from the immaterial and to distinguish the primary from the 

 newly acquired. 



Among the Metazoa such an attempt is useless, since even 

 the least complicated form of asexual reproduction whicli 

 occurs in this group, the simple breaking up of Lumbriculus, 

 exhibits phenomena (regeneration) in connexion with the 

 multiplication which at once exclude the possibility of identi- 

 fying the process with the fission of inorganic bodies. 



With regard to the Protozoa the case is different : here we 

 actually find the desired starting-point. The fission of an 

 Amoeba coincides exactly as regards the outward phenomenon 

 and its consequences with that of the block of stone or 

 crystal : the process itself and the relations to size, time, and 

 growth are the same in each case. The only difference is 

 objective and does not affect our argument ; it lies in the fact 

 that the effect, which in the case of the block of stone is 

 produced by the hand of man from the outside, results in the 

 Amoeba from internal causes having their origin in the 

 organism itself. 



Since, therefore, both instances of fission are similar pro- 

 cesses, the fission of the Amoeba also consists in the actual 

 process of division. I will term this simplest form of fission, 

 which we may also hold to be the earliest, " architomy " (i. e. 

 " primary form of fission ") . 



Nevertheless among the modes of reproduction found in 

 the Protozoa there are also some which appear to diverge 

 considerably from the architomic type, and y%\ from the 

 earliest times they have been declared without contradiction 

 to be instances of fission. We will briefly consider two of 

 these cases. 



The reproduction of certain Infusoria takes place in such a 

 way that an envelope or cyst is differentiated within which 

 the processes of fission are carried out. The latter, considered 

 by themselves, belong to the architomic class ; but in con- 

 nexion with them we get the further phenomenon of the 

 above-mentioned formation of the envelope. Clearly the true 

 question which is here raised is this : Is the formation of a 

 cyst the expression of a new principle, when contrasted with 

 which the fission becomes of secondary importance, or may 

 we interpret it as an adaptation of one of those vital pheno- 

 mena otherwise known to us in these animals, which is here 

 brought into harmony with and subordinated to the process 

 of fission ? There never was any doubt about rejecting the 



