VARIATION UNDER NATURE 47 



common oak, how closely it has been studied ; yet a 

 German author makes more than a dozen species out of 

 forms, which are very generally considered as varieties ; 

 and in this country the highest botanical authorities 

 and practical men can be quoted to show that the 

 sessile and pedunculated oaks are either good and 

 distinct species or mere varieties. 



When a young naturalist commences the study of 

 a group of organisms quite unknown to him, he is at 

 first much perplexed to determine what differences to 

 consider as specific, and what as varieties ; for he 

 knows 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 

 knowledge of analogical variation in other groups and 

 in other countries, by which to correct his first impres- 

 sions. 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, Jh.e 

 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 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 



