324 ON THE PHENOMENA OF GEMMATION 



to that exhibited by Aphis in the animal and vegetable worlds, but 

 if we look closely into the matter, agamogenesis is found to pass by 

 insensible gradations into the commonest phenomena of life. All 

 life, in fact, is accompanied by incessant growth and metamorphosis ; 

 and every animal and plant above the very lowest attains its adult 

 form by the development of a succession of buds. When these 

 buds remain connected together, we do not distinguish the process 

 as anything remarkable ; when, on the other hand, they become 

 detached and live independently, we have agamogenesis. Why 

 some buds assume one form and some another, why some remain 

 attached and some become detached, we know not. Such phenomena 

 are for the present the ultimate facts of biological science ; and as we 

 cannot understand the simplest among them, it would seem useless, 

 as yet, to seek for an explanation of the more complex. 



Nevertheless, an explanation of agamogenesis in the Aphis and in 

 like cases has been offered. It has been supposed to depend upon 

 " the retention unchanged of some part of the primitive germ-mass ; " 

 this germ-mass being imagined to be the seat of a peculiar force, by 

 virtue of which it gives rise to independent organisms. 



There are however two objections to this hypothesis : in the first 

 place, it is at direct variance with the results of observation ; in the 

 second, even if it were true, it does not help us to understand the 

 phenomena. With regard to the former point, the hypothesis pro- 

 fesses to be based upon only two direct observations, one upon Aphis, 

 the other upon Hydra ; and both these observations are erroneous, 

 for in neither of these animals is any portion of the primitive germ- 

 mass retained, as it is said to be, in that part which is the seat of 

 agamogenesis. 



But suppose the fact to be as the hypothesis requires ; imagine 

 that the terminal chamber of the pseudovarium is full of nothing 

 but " unaltered germ-cells ; " how does this explain the phenomena ? 

 Structures having quite as great claim to the title of " unaltered germ 

 cells " lie in the extremities of the acini of the secreting glands, in the 

 sub-epidermal tissues and elsewhere ; why do not they give rise to 

 young ? Cells, less changed than those of the pseudovarium of Aphis, 

 and more directly derived from the primitive germ-mass, underlie the 

 epidermis of one's hand , nevertheless, no one feels any alarm lest a 

 nascent wart should turn out to be an heir. 



On the whole, it would seem better, when one is ignorant, to 

 say so, and not to retard the progress of sound inquiry by inventing 

 hypotheses involving the assumption of structures which have no 

 existence, and of " forces " which, their laws being undetermined, 

 are merely verbal entities. 



