EIGHTEENTH CENTURY EVOLUTIONISTS 207 



\nomia} In this chapter he combats Bonnet's 

 apctrine of emboitcmcnt or Evolution, and de- 

 ir)nds the idea of individual development by suc- 

 pgssive additions of parts to the embryo, but in 

 im original formation of the embryo he rejects 

 tha pangenesis theory of BufFon, that is, of the 

 of ri^S^^i^^ o^ 1^^^ parts from the two parents. 

 jQus^'^se organic particles he [Buffon] supposes 

 fjn^e ist in the spermatic fluids of both sexes, and 

 in sii^^^y ^^^ derived thither from every part of 

 inff ^ody, and must therefore resemble, as he sup- 

 (jgses, the parts from whence they are derived." 

 le substitutes for this a theory of his own, of the 

 addition of parts, which takes little account of 

 che law^s of heredity. 



The individual life begins or develops, as all 

 life originally began, from a single filament.^ 

 "Shall we conjecture," he says, "that one and the 

 same kind of living filament is and has been the 

 cause of all organic life? ... I suppose this liv- 

 ing filament, of whatever form it may be, whether 

 sphere, cube, or cylinder, to be endued with 

 the capability of being excited into action by cer- 

 tain kinds of stimulus." This irritability and ex- 

 citability is the first step in Darwin's concep- 

 tion of Evolution. It is that whereby animals 

 and plants react to their environment, causing 



^ Zoonomia, vol. 1, xxxix. 



"^Compare the cell theory of Schlelden and Schwann. 



