- evr EVOLUTION IN BIOLOGY 191 
Bonnet affirms that, before fecundation, the hen’s 
egg contains an excessively minute but complete 
chick ; and that fecundation and incubation simply 
cause this germ to absorb nutritious matters, which 
are deposited in the interstices of the elementary 
structures of which the miniature chick, or germ, 
ismade up. The consequence of this intussuscep- 
__ tive growth is the “ development ” or “evolution” 
_ of the germ into the visible bird. Thusan organ- 
ised individual (tout organisé) “is acomposite body 
‘consisting of the original, or elementary, parts and 
of the matters which have been associated with 
them by the aid of nutrition;” so that, if these 
matters could be extracted from the individual 
(tout), it would, so to speak, become concentrated 
in a point, and would thus be restored to its 
primitive condition of a germ ; “just as by extract- 
ing from a bone the calcareous substance which is 
the source of its hardness, it is reduced to its 
primitive state of gristle or membrane.” ! 
“Evolution” and “development” are, for 
Bonnet, synonymous terms ; and since by “ evolu- 
tion” he means simply the expansion of that 
- which was invisible into visibility, he was natur- 
ally led to the conclusion, at which Leibnitz had 
arrived by a different line of reasoning, that no 
such thing as generation, in the proper sense of 
the word, exists in Nature. The growth of an 
' Considérations sur les Corps organisés, chap. x. 
