204 EVOLUTION IN BIOLOGY vi 



from the female parent ; and that, regarded as a 

 mass of molecules, the entire organism may be com- 

 pared to a web of which the warp is derived from the 

 female and the woof from the male. And each of 

 these may constitute one individuality, in the same 

 sense as the whole organism is one individual, al- 

 though the matter of the organism has been con- 

 stantly changing. The primitive male and female 

 molecules may play the part of Buffon's " moules 

 organiques," and mould the assimilated nutriment, 

 each according to its own type, into innumerable 

 new molecules. From this point of view the process, 

 which, in its superficial aspect, is epigenesis, appears 

 in essence, to be evolution, in the modified sense 

 adopted in Bonnet's later writings ; and develop- 

 ment is merely the expansion of a potential organ- 

 ism or " original preformation " according to fixed 

 laws. 



II. The Evolution of the Sum of Living Beings. 



The notion that all the kinds of animals and 

 plants may have come into existence by the growth 

 and modification of primordial germs is as old as 

 speculative thought; but the modern scientific 

 form of the doctrine can be traced historically to 

 the influence of several converging lines of philo- 

 sophical speculation and of physical observation, 

 none of which go farther back than the seven- 

 teenth century. These are : 



