Xo. 49(iJ ASPECTS OF THE SPECIES QUESTION 229 



This idea proceeds on tlie supposition that the species 

 which we know have existed as long as the earth has had 

 its present form. No doubt there were, in tlie i)r('ceding 

 state of our globe, other species of plants, which have 

 now perished, and the remains of which we still find in 

 impressions in shale, slate-clay, and other thvtz rocks. 

 Whether the present species, which often resemble these, 

 have arisen from them ; whether the great revolutions on 

 the surface of the earth, which we read in the Book of 

 Xature, contributed to these transitions— we know not. 

 AVliat we know is that from as early a time as the human 

 race has left memorials of its existence upon the earth 

 the separate species of plants have maintained the same 

 properties invariably. 



To be sure, w^e frequently speak of the transitions and 

 crossings of species ; and it can not be denied that some- 

 thing of this kind does occur, though without affecting 

 the idea of sj^ecies which we have proposed. We must, 

 therefore, understand this difference. 



AVe perceive the Transitions of a Species, when it loses 

 or changes the properties, which we had considered as 

 invariable in the character. Thus, it would be a transi- 

 tion, if we had stated as an invariable character of winter 

 wheat (Triticum liyhernum), that it was biennial, and 

 had an ear without awns ; and if we should remark, that 

 by frequent reproduction, and by very different treat- 

 ment, it began to assume awns, and, when sown in spring, 

 came to maturity during the same sunnner. 



But this shows only that our idea of the difference 

 between the two kinds of grains had been incorrect ; for 

 ' it is the universal rule, that the character does not con- 

 stitute the species, but the species the character. Species, 

 then, only appear to undergo transitions, when we have 

 considered an organ or a property as invariable which 

 is not so. 



All properties of plants which are subject to change, 

 fonii either a subspecies or a variety. By the foimer 

 we understand such forms as continue indeed during 



