Cnxr. II. DOUBTFUL SPECIES. 61 



admitted species which closely surround the typical Qucnuis 

 rol)ur. Finally, De Candolle admits that, out of the three hun- 

 dred species, Avhicli will l^e enumerated in his Prodromus as 

 belonging to the oak family, at least two-thirds are provisional 

 species, that is, are not known strictly to fulfil the definition 

 above given of a true species. For it should be added that De 

 Candolle no longer believes that species are immutable crea- 

 tions, but concludes that the derivative theory of the succession 

 of forms is the most natural one, " and the most accordant with 

 tlie known facts in paleontology, geographical botany and zo- 

 ology, of anatomical structure and classification ; " but, he adds, 

 direct proof is still wanting. 



When a young naturalist commences the study of a group 

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

 plexed to determine what difiercnces to consider as specific, and 

 what as varietal ; 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 l)eforc 

 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 corrett his first impressions. As he extends the 

 range of his oljservations, he will meet Avith more cases of diffi- 

 culty ; for ho will encounter a greater number of closely-allied 

 forms. But if his observations be widely extended, he will in 

 the end generally l)e enaljled to make up his own mind which 

 to call varieties and wliich 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. 

 AV'hen, moreover, he comes to study allied forms brought from 

 countries not now continuous, in which case he cannot hope to 

 find tlie intermediate links between his doubtful forms, he will 

 have to trust almost entirely to analog}-, and his difliculties rise 

 to a climax. 



Certainl}^ no clear line of demarcation has as yet been drawn 

 between species and sub-sju^cies — that is, the forms which in 

 the ojjinion 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 



