Chap. II. DOUBTFUL SPECIES. 51 



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 knowledge of analogical variation in 

 other groups and in other countries, by which to correct 

 Ins 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 observations be widely extended, he 

 will in the end generally be enabled to make up his own 

 mind which to call varieties and which species ; 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, moreover, he 

 comes to study allied forms brought from countries not 

 now continuous, in which case he can hardly hope to 

 find the intermediate links between his doubtful forms, 

 he will have 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 dif- 

 ferences. These differences blend into each other in an 

 insensible series ; and a series impresses the mind with 

 the idea of an actual passage. 



Hence I look at individual differences, though of 

 small interest to the systematist, as of high importance 

 for us, as being the first step towards such slight varieties 

 as are barely thought worth recording in works on natural 

 history. And I look at varieties which are in any degree 

 more distinct and permanent, as steps leading to more 



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