64 DOUBTFUL SPECIES. [Chap. IL 



nothing of the amount and kind of variation to which 

 the group is subject; and this shows, at least, how very 

 generally there is some variation. But if he confine 

 his attention to one class within one country, he will 

 soon make up his mind how to rank most of the doubt- 

 ful forms. His general tendency will be to make many 

 species, for he will become impressed, just like the 

 pigeon or poultry fancier before alluded to, with the 

 amount of difference in the forms which he is continu- 

 ally studying; and he has little general knowledge of an- 

 alogical variation in other groups and in other coun- 

 tries, by which to correct his first impressions. As 

 he extends the range of his observations, he will meet 

 with more cases of difficulty; for he will encounter a 

 greater number of closely-allied forms. But if his ob- 

 servations be widely extended, he will in the end gen- 

 erally be able to make up his own mind: but he will 

 succeed in this at the expense of admitting much varia- 

 tion, — and the truth of this admission will often be 

 disputed by other naturalists. When he comes to study 

 allied forms brought from countries not now continu- 

 ous, in which case he cannot hope to find intermediate 

 links, he will be compelled to trust almost en- 

 tirely to analogy, and his difficulties will rise to a 

 climax. 



Certainly no clear line of demarcation has as yet 

 been drawn between species and sub-species— that is, 

 the forms which in the opinion of some naturalists 

 come very near to, but do not quite arrive at, the rank 

 of species: or, again, between sub-species and well- 

 marked varieties, or between lesser varieties and 

 individual differences. These differences blend into 

 each other by an insensible series; and a series 



