32 EX VIRIBUS VIVIMUS. 



physiological units of Mr. Herbert Spencer, which he 

 describes as follows/ will suffice as an assumption ; 

 or, indeed, we need go no further in explicitness 

 than is involved in the assumption of 'a matter of 

 life.' What we have to explain is why Mr. Spencer's 

 units, or the ' matter of life,' should be limited in 

 quantity in various organisms, so that life terminates 

 at different periods, even when two species compared 

 appear to have been subjected to the same external 

 agencies. The old writers distinguished the ' vires in 

 posse ' and the ' vires in actu.' The aged, they said, 



factory to do. The material character seems also some objection to 

 these gemmules. For take the case of a polyp reproducing asexually 

 for three thousand years. According to Mr. Darwin's supposition, 

 involved in his explanation of Atavism and Reversion, the last genera- 

 tion of polyps contain gemmules from every preceding generation. The 

 persistence of the same material gemmule, and the vast increase in the 

 number of gemmules, and consequently of material bulk, as later 

 generations come on, make a material theory difficult. Modified force- 

 centres, becoming further modified in each generation, such as Mr. 

 Spencer's physiological units, might be made to fit in with Mr. Darwin's 

 hypothesis in other respects. 



^ Mr. Spencer, after describing the organic 'polarity' seen in the 

 phenomena of repair and development, says, ' If then this organic 

 polarity can be possessed neither by the chemical units nor the mor- 

 phological units, we must conceive it as possessed by certain intermediate 

 units, which we may term phyiiological. There seems no alternative but 

 to suppose that the chemical units combine into units immensely more 

 complex than themselves, complex as they are ; and that in each 

 organism, the physiological units produced by this further compounding 

 of highly compound atoms, have a more or less distinctive character. 

 We must conclude that in each case, some slight difference in their 

 mutual play of forces produces a difference in the form which the 

 aggregate of them assumes.' 



