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 

 doubtful 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 

 continually studying ; and he has little general know- 

 ledge of analogical variation in other groups and in other 

 countries, by which to correct his first impressions. 

 As he extends the ran^e 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 

 observations be widely extended, he will in the end 

 generally be able to make up his own mind : but he 

 will succeed in this at the expense of admitting much 

 variation, — 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 

 continuous, in which case he cannot hope to find 

 intermediate links, he will be compelled to trust 

 almost entirely 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 



