OTHER THEORIES OF SPECIES-FORMING. 34* 



say: "Linnaeus himself knew that in some cases all sub- 

 divisions of a species are of equal rank, together constituting 

 the group called species. No one of them outranks the 

 others; it is not a species with varieties, but a group con- 

 sisting only of varieties. A closer inquiry into the cases 

 treated in this manner by the great master of systematic 

 science shows that here his varieties were exactly what we 

 now call 'elementary species. 



"In other cases the varieties are of a derivative nature. 

 The species constitutes a type that is pure in a race which 

 ordinarily is still growing somewhere, though in some cases 

 it may have died out. From this type the varieties are 

 derived, and the way of this derivation is usually quite 

 manifest to the botanist. It is ordinarily by the disappear- 

 ance of some superficial character that a variety is dis- 

 tinguished from its species, as by the lack of colour in the 

 flowers, of hairs on stems and foliage, of the spines and 

 thorns, etc. Such varieties are, strictly speaking, not to be 

 treated in the same way as elementary species, though they 

 often are. We shall designate them by the term of 'retro- 

 grade varieties/ which clearly indicates the nature of their 

 relationship to the species from w r hich they are assumed to 

 have sprung. In order to lay more stress on the contrast 

 between elementary species and retrograde varieties, it 

 should be stated at once, that the first are considered to 

 have originated from their parent-form in a progressive 

 way. They have succeeded in attaining something quite 

 new for themselves, while retrograde varieties have only 

 thrown off some peculiarity, previously acquired by their 

 ancestors." : 



With regard to the facts and general evidence 20 on which 

 _, de Vries bases his beliefs and theory a few 



The facts at 



basis of de words, too few, I regret, must suffice. Like 



Vries's theory, Darwill) de V ries only came to the full pub- 

 lication of his theory after many years of assiduous obser- 



