EVOLUTION IN NATURE AND UNDER DOMESTICATION. 243 



the possibility of their survival. New species in these organisms 

 can establish themselves in the territory of their parent species, 

 living in identically the same circumstances, fitting in the 

 same ecological niche. 



The biological law proposed by the zoologist Jordan, that 

 closely related species will be found either in different terri- 

 tory, or fitting different ecological niches in the same territory 

 holds good only for allogamous organisms. In making his gener- 

 alization he did not consider such species as we know in autog- 

 amous plants, and as were first demonstrated by the botanist 

 Jordan. 



Species formation in allogamous organisms is a process of 

 colonization. Evolution, the establishment of new species in 

 allogamous organisms is practically impossible within the same 

 territory and the same ecological niche already occupied by a 

 species. When a certain number of individuals of a species colon- 

 ize in a place where conditions are right for them, the barriers 

 separating the new group from the multitude of the species 

 may be strong enough, and (or) the rate of disperal of the or- 

 ganisms may be slow enough, to make matings within the 

 group far more common than matings with individuals of the 

 old species. If this is the case, the possibility exists for the 

 origin of a new local species. The potential variability of the 

 new group will reduce itself, and the final type may be the 

 original type of the species, in which case we again have a case 

 of colonization. But the final type may also be somewhat differ- 

 ent, if the potential variability allows of this. The new group 

 may have a slightly different size or colour or shape, or rate of 

 reproduction. Natural selection may have had nothing to 

 do with the final type of the new species. The new characters 

 need not be of any advantage or adapt the organism any better 

 to its surroundings. In a study of the smaller mammals, and of 

 birds, such local species which differ in trivial characters, and 

 occur in the same ecological position but in different regions 

 have been found to be the rule. The American zoologists have 

 collected valuable data on this point. 



