174 THE BEGINNINGS OF LIFE. 



of the older naturalists and physiologists who have 

 written during the last hundred years. We shall thus 

 see how strong the belief in the truth of this doctrine 

 has been, amongst many of those whose opinions car- 

 ried great weight in their time. 



Commencing with Needham, the English champion 

 of heterogeny during the last century, we find him 

 maintaining a belief in the essential oneness of the 

 living force or vital principle of both animals and 

 plants — ^ force ^vigetattve^ as he called it. This, he 

 thought, always survived after the death of the par- 

 ticular animals and plants in which it had previously 

 been the guiding principle. Restricted in its operations 

 during the life of the individual — that is, acting 

 in a determinate way in each given organism — it- 

 assumes more freedom of action after the death of 

 the organism. Still residing, however, in the organic 

 matter, it forces the complex molecules of such ma- 

 terials to enter into new Miving' combinations — the 

 actual nature of these, and, consequently, of the re- 

 sulting living things, being dependent upon the con- 

 ditions in which the organic matter is placed and the 

 particular sets of physical influences to which it is 

 subjected i. 



It will be seen that this is an essentially spiritualistic 

 conception. We shall find, however, that Buffon, who 

 was for a time associated with Needham, and who was 



' See Spallanzani's • Opuscules,' Exposition des nouvelles idees de 

 M. de Needham sur la systfeme de la generation, t. i^r, chap. !«•■. 



