284 LAMARCK, HIS LIFE AND WORK 



which circumstances have forced to change in climate, 

 mode of life, and habits ; but in their case the in- 

 fluences of the causes which I have just cited need 

 still more time than the plants to bring about notable 

 changes in the individuals. 



" The idea of embracing, under the name of species, 

 a collection of like individuals which are perpetuated 

 by generation, and which have remained the same as 

 long as nature has endured, implies the necessity 

 that the individuals of one and the same species 

 should not cross with individuals of a different species. 



" Unfortunately observation has proved, and still 

 proves every day, that this consideration is un- 

 founded ; for hybrids, very common among plants, 

 and the pairings which we often observe between the 

 individuals of very different species of animals, have 

 led us to see that the limits between these supposed 

 constant species are not so fixed as has been imagined. 



" In truth, nothing often results from these singu- 

 lar unions, especially if they are very ill-assorted, and 

 then the individuals which do result from them are 

 usually infertile ; but also, when the disparities are 

 less great, we know that the default in question does 

 not occur. 



" But this cause only suffices to create, step by 

 step, varieties which finally become races, and which, 

 with time, constitute what we call species. 



" To decide whether the idea which is formed of 

 the species has any real foundation, let us return to 

 the considerations which I have already explained ; 

 they lead us to see : 



" I. That all the organized bodies of our globe are 

 true productions of Nature, which she has succes- 

 sively formed after the lapse of much time ; 



" 2. That, in her course. Nature has begun, and 

 begins over again every day, to form the simplest or- 

 ganisms, and that she directly creates only those, 

 namely, which are the first germs {dbauches) of organ- 



