CHAPTER IX 

 SPECIES IN THE MAKING 



A SERIES of important conceptions are implied in 

 the word " species," as used by naturalists. Some 

 of these we have noted in the last chapter. There 

 is first, as a starting-point, the conception that a species 

 is a number or company of individuals, all closely and 

 clearly alike (though presenting some minor individual 

 variations), and capable of sharp separation by certain 

 "characters" from other similar groups or companies. 

 Then follows the addition (2) that the species is constant 

 if the conditions of life are not changed, or but little 

 changed, and that year after year it reproduces itself 

 without change. It has a certain stability (but not 

 permanent immutability) greater in some species than in 

 others. Next we find (3) that the species constitutes a 

 group of individuals which have descended by natural 

 breeding from common parents, not differing greatly from 

 the present individuals. They are, in fact, one " stock." 

 Then (4) that the species is a group, the individuals of 

 which pair with one another in breeding, but do not pair 

 with the individuals of another species, and that this is 

 due to various peculiar and inherent chemical, physio- 

 logical and (in higher animals) psychological characteristics 

 of the species. 



We have now further to note that species have their 

 special geographical centi'es of origin from which most 



spread only a small distance, whilst others have a 



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