Fission and Gemmation in the Animal Kingdom. 31 



which happens to take place concurrently with fission and 

 which I previously neglected for the sake of simplicity, offers 

 no peculiarity, the growth which leads to the formation of a 

 bud in Podojihrya differs from the very first from tlie normal 

 increase in size in this Acinetarian. The growth of the 

 Acinctarian buds is limited in extent to isolated spots on the 

 surface of the body of the budding parent-form : it is not the 

 groivth of the Podophrya, hut a growth upon it, by the side of 

 which the former continues, or may continue, to exist. 



It is advisable, for the sake of simplifying matters, to 

 sharply distinguish this bud-growth under the title " differ- 

 entiaV from the normal or " individual ''^ growth. 



Differential growth appears to a certain extent as trans- 

 cending the organization and personality of the budding 

 parent- form, and therefore implies no increase of size for the 

 latter ; precisely on this account it necessarily leads to the 

 production of a new individual : in its simplest form it in no 

 way affects the organization and individuality of the budding 

 animal, as, for instance, is manifest in the case of Hydra. 

 As opposed to this, individual growth entails an actual increase 

 in the size of the animal which is sooner or later to divide ; 

 but this coincides with the form of growth which belongs to 

 this organism, since it actually represents nothing more than 

 the natural increase in size {normal growth) of tlie creature 

 in question, whether simultaneously or subsequently asexual 

 reproduction sets in or not. 



In this connexion also I would at the same time emphati- 

 cally point out that it is not the direction of growth which 

 constitutes the entire difference, as it might appear on a super- 

 ficial consideration of the circumstances of asexual reproduc- 

 tion. As a matter of fact the buds of Acinetarians also make 

 this clear, since their growth essentially takes place in the 

 normal direction of that of the parent, and yet in no way 

 represents a simple increase in the size of the latter. 



The multiplication of Acinetarians thus proves itself to be 

 a form of reproduction which differs from fission, and is in its 

 essence solely and sufficiently determined hy the appearance of 

 a special form of growth, which we have termed differential. 

 This peculiarity is certainly important enough to warrant our 

 designating such processes by a special name : I merely 

 follow old custom in embracing them under the comprehen- 

 sive term ^^ gemmation.''^ 



That which reminds us of fission in these cases is simply 

 the process — the severance — by which the bud becomes a 

 free independent being, an act within this asexual mode of 

 reproduction, which is far more often omitted than performed. 



