44 DOUBTFUL SPECIES. 



habit distiact continents or islands. When, on the other 

 hand, an animal or plant ranges over the same continent, 

 or inhabits many islands in the same archipelago, and pre- 

 sents different forms in the different areas, there is always ?, 

 good chance that intermediate forms will be discovered which 

 will link together the extreme states ; and these are then 

 degraded to the rank of varieties. 



Some few naturalists maintain that animals never present 

 varieties ; but then these same naturalists rank the slightest 

 difference as of specific value ; and when the same identical 

 form is met with in two distant countries, or in two geologi- 

 cal formations, they believe that two distinct species are 

 hidden under the same dress. The term species thus comes 

 to be a mere useless abstraction, implying and assuming a 

 separate act of creation. It is certain that many forms, con- 

 sidered by highly competent judges to be varieties, resemble 

 species so completely in character that they have been thus 

 ranked by other highly competent judges. But to discuss 

 whether they ought to be be called species or varieties, 

 before any definition of these terms has been generally 

 accepted, is vainly to beat the air. 



Many of the cases of strongly marked varieties or doubtful 

 species well deserve consideration ; for several interesting 

 lines of argument, from geographical distribution, analogical 

 variation, hybridism, etc., have been brought to bear in the 

 attempt to determine their rank ; but space does not here 

 permit me to discuss them. Close investigation, in many 

 cases, will no doubt bring naturalists to agree how to rank 

 doubtful forms. Yet it must be confessed that it is in the 

 best known countries that we find the greatest number of 

 them. I have been struck with the fact that if any animal 

 or plant in a state of nature be highly useful to man, or 

 from any cause closely attracts his attention, varieties of it 

 will almost universally be found recorded. These varieties^ 

 moreover, will often be ranked by some authors as species. 

 Look at the common oak, how closely it has been studied ; 

 yet a German author makes more than a dozen species out 

 of forms, which are almost universally considered by other 

 botanists to be 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. 



I may here allude to a remarkable memoir lately pub- 

 lished by A. de Candolle, on the oaks of the whole world 



