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.^ 

 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 OcnotJicra 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 



^ R. V. Wettstein, Dcr Saison-DimorpJiis)nus aJs Ansgangspunkt 

 fib' die Bildung nciicr Artcn im Pftanccnrcich, Ber. d. d. bot. Ges., 

 Vol. XIII, 1895, p. 303 ; and particularly the same author's Desccn- 

 denztheoretische Untersiichungen; I. Unfersuclmngen i'tbcr den Sai- 

 son-Dimorphismiis im Pftanzenreich; Denkschr. d. ]\Iat. Naturvv. 

 Classe d. k. Akad. d. Wiss., Vienna, 1900. 



