THE FUNDAMENTAL CHARACTERISTIC OF LIFE. 411 



part is but a repetition of every other, are differentiated in 

 the highest amongst a variety of organs, acquiring in virtue 

 of this differentiation a much greater intensity. 



Thus, then, we may take that mode of Vital Activity 

 which manifests itself in the evolution of the germ into the 

 complete organism repeating the type of its parent, and the 

 subsequent maintenance of that organism in its integrity, in 

 the one case as in the other, at the expense of materials de- 

 rived from external sources as the most universal and most 

 fundamental characteristic of Life ; and we have now to con- 

 sider the nature and source of the Force or Power by which 

 that evolution is brought about. The prevalent opinion has 

 until lately been, that this power is inherent in the germ ; 

 which has been supposed to derive from its parent not merely 

 its material substance, but a nisus formativus, bildungstrieb, 

 or germ force, in virtue of which it builds itself up into the 

 likeness of its parent, and maintains itself in that likeness 

 until the force is exhausted, at the same time imparting a 

 fraction of it to each of its progeny. In this mode of view- 

 ing the subject, all the organizing force required to build up 

 an Oak or a Palm, an Elephant or a Whale, must be concen- 

 trated in a minute particle, only discernible by microscopic 

 aid, and the aggregate of all the germ-forces appertaining to 

 the descendants, however numerous, of a common parentage, 

 must have existed in their original progenitors. Thus in the 

 case of the successive viviparous broods of Aphides, a germ- 

 force capable of organizing a mass of living, structure, which 

 would amount (it has been calculated)* in the tenth brood 

 to the bulk of five hundred millions of stout men, must have 

 been shut up in the single individual, weighing perhaps the 

 l-1000th of a grain, from which the first brood was evolved. 

 And in like manner, the germ-force which has organized the 



* See Prof. Huxley on the " Agamic Reproduction of Aphis," in Linn. 

 Trans., vol. xxii., p. 215. 



