PERPETUATION OF LIVING BEINGS 89 



recognizable by those who fish in the particular streams. 

 There is the same differences in leeches ; leech collectors 

 can easily point out to you the differences and the 

 peculiarities which you yourself would probably pass by ; 

 so with fresh-water mussels ; so, in fact, with every animal 

 you can mention. 



In plants there is the same kind of variation. Take 

 such a case even as the common bramble. The botanists 

 are all at war about it ; some of them wanting to make out 

 that there are many species of it, and others maintaining 

 that they are but many varieties of one species ; and they 

 cannot settle to this day which is a species and which is a 

 variety I 



So that there can be no doubt whatsoever that any plant 

 and any animal may vary in nature ; that varieties may 

 arise in the way I have described, as spontaneous varieties, 

 and that those varieties may be perpetuated in the same 

 way that I have shown you spontaneous varieties are 

 perpetuated ; I say, therefore, that there can be no 

 doubt as to the origin and perpetuation of varieties in 

 nature, 



But the question now is : Does selection take place in 

 nature ? is there anything like the operation of man in 

 exercising selective breeding, taking place in nature ? 

 You will observe that, at present, I say nothing about 

 species ; I wish to confine myself to the consideration of 

 the production of those natural races which everybody 

 admits to exist. The question is, whether in nature there 

 are causes competent to produce races, just in the same 

 way as man is able to produce, by selection, such races of 

 animals as we have already noticed. 



When a variety has arisen, the CONDITIONS OF EXIST- 

 ENCE are such as to exercise an influence which is exactly 

 comparable to that of artificial selection. By Conditions 

 of Existence I mean two things, there are conditions 

 which are furnished by the physical, the inorganic world, 

 and there are conditions of existence which are furnished 

 by the organic world. There is, in the first place, CLIMATE ; 

 under that head I include only temperature and the varied 

 amount of moisture of particular places. In the next 

 place there is what is technically called STATION, which 

 means given the climate, the particular kind of place in 

 which an animal or a plant lives or grows ; for example, the 

 station of a fish is in the water, of a fresh-water fish in 



