46 DOUBTFUL SPECIES. 



When a young naturalist commences the study of a group 

 of organisms quite unknown to him, he is at first much 

 perplexed in determining what differences to consider as 

 specific and what as varietal ; for he knows nothing of the 

 amount and kind of variation to which the group is sub- 

 ject ; 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, 

 Avith 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 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 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 coun- 

 tries 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 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 the highest importance for 

 us, as being the first steps toward 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 toward more strongly 

 marked and permanent varieties ; and at the latter, as 

 leading to sub-species and then to species. The passage 

 from one stage of difference to another may, in many cases, 



