Fission and Gemmation in the Animal Kingdom. 47 



viduality (biul), and this then separates completely or incom- 

 pletely from the parent individual without the latter's own 

 individuality being thereby destroyed. Therefore in this 

 case the two products of fission are of unequal value." 

 Ha?ckel further proceeds to show that fission produces indi- 

 viduals of the same age, whereby the original animal as such 

 is abolished, while the products of gemmation are of different 

 ages, and the budding animal continues to exist unaltered as 

 the parent form *. 



These assertions, the artificial construction of which is 

 unmistakable, met with just contradiction on the extension 

 of our knowledge of the processes in question. Thus Goette 

 took the special case of the strobilation of Aiirelia aurita as 

 the starting-point of a critical excursus, in which he in the 

 first place alludes to the fact that the products of gemmation 

 resemble the parent form far more often than do tliose of 

 fission. He then goes on to say : " What Hseckel moreover 

 means by the unequal age of the products of gemmation is 

 shown by the application to the case of Strobila which follows 

 upon the iieels of the definition ; for he says that the disks of 

 the Strobila arise one after the other, and so possess that 

 inequality of age which is the characteristic of gemmation. 

 He therefore refers in this case not to the difference in age 

 between the products of division due to one individual process 

 of gemmation, but rather to the different age of the disks 

 which follow one another in succession. Precisely the same 

 difference of age exists, however, in all successive fissions of 

 the same animal, such as, for instance, appear so conspicu- 

 ously in Microstoma ; it is therefore quite useless as a distinc- 

 tive characteristic of gemmation. 



"Just as untrustworthy is, lastly, the characteristic of 

 growth, in the one case total (fission), in the other only 

 partial (gemmation) ; for, apart from the frequent difficulty 

 of such a distinction, we are in no wise justified by expe- 

 rience in declaring a growth at all to be the necessary cause 

 of every division." 



Goette, therefore, is unable to recognize as applicable and 

 suflScient the distinguishing characters of fission and gemma- 

 tion laid down by Hseckel, and for his part defines fission as 

 a " separation of connected parts, which were therefore 

 already present in a fully developed state," but gemmation as 

 a " new formation of parts by the method of a local growth, 

 which become more or less independent " f. 



* E. Hfeckel, * Generelle Morpliologie der Organismen/ Bd. 2, Berlin, 

 1866, pp. 37 et sqq. 



t A. Goette, ojy. tit. pp. 47 et sqq. 



