274 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



been drawn by the researches of Nilsson and of 

 Hugo de Vries. Indeed, the hypothesis of varia- 

 tion of species by sudden skips is of very ancient 

 date. Already very clearly perceived by Isidore 

 Geonroy-Saint-Hilaire, it was adopted and cham- 

 pioned by Haldemann, Cope, Dollo, and many 

 other palaeontologists. These last especially saw 

 in it a convenient way of explaining on other lines 

 than by the rather worn-out and eternal argument 

 of the insufficiency of palseontological documents, 

 the sudden apparitions of groups and the absence 

 of transitional forms, which are such frequent and, 

 if one might say so, such general phenomena in the 

 history of the development of fossil animals. But, 

 it has to be acknowledged, that saltation has always 

 remained in the realm of palaeontology a simple 

 theoretical hypothesis without any sanction of real 

 and demonstrative fact. It is no longer permissible 

 now to address this criticism to the curious researches 

 made on the sudden variation of some of our present 

 vegetables. 



The starting-point of the experiments of de Vries 

 has been the cultivation of abnormal or monstrous 

 varieties of certain wild plants. The Carder e * gave 

 him, in particular, a variety with a spiral stem, 

 whose embryo is distinguishable from the normal 

 type by three cotyledons instead of two. This 

 twisted variety, which appears accidentally and in 

 a sudden manner, is kept up by heredity. But the 

 leading discoveries of the Amsterdam professor 

 have been effected on the (Enotheras, garden 



* Diysacus: Anglic^ teazle, 



