III. THE DIFFERENT MODES OF ORIGIN OF 
NEW SPECIES, 
6. HORTICULTURAL AND SYSTEMATIC VARIETIES 
AND ELEMENTARY SPECIES. 
The opinion has of late been often expressed, by VON 
WETTSTEIN in particular, that there is no ground for the 
assumption that all species have arisen in the same way. 1 
There is no difficulty in applying this view to the theory 
of mutation, although one of the chief objects of this 
book is to show that ordinary or fluctuating variability 
does not provide material for the origin of new species. 
But this does not exclude the possibility of different 
modes of origin of new species. The simultaneous origin 
of species in groups, in definite periods, such as I have 
described in the case of Ocnothcra Lainarckiana, must 
constitute for me the main type of this process, until the 
origin of species has been experimentally studied in other 
cases. Such experiments would have to study the phe- 
nomenon before and during the first appearance of the 
new type. Inferences drawn from data obtained after its 
appearance can hardly be considered as decisive. 
This essential type explains in my opinion in the first 
1 R. v. WETTSTEIN, Der Saison-Dimorpliismus ah Ausgangspunkt 
fiir die Bildung neuer Artcn im Pflanzenrcich, Ber. d. cl. hot. Ges., 
Vol. XIII, 1895, P- 3O3 ; and particularly the same author's Desccn- 
denztheoretische Untersuc/ningcii; I. Untersuchungen iibcr den Sai- 
son-Dimorphismus im Pflanzenrcich; Denkschr. d. Mat. Naturw. 
Classe d. k. Akad. d. Wiss., Vienna, 1900. 
