718 president's address. 



live again for a long period in a state of stability, till they again, 

 in their turn, overlive themselves and break up again into new 

 forms. And so the development in Fauna and Flora goes on 

 from millions of years back to the present time, long periods 

 of stability always alternating with shorter mutation-periods. 

 According to this theory, the species would be again a finished 

 unit, not a finished created species as understood by the pre- 

 Darwin naturalists, but a finished unit at least for a certain 

 period. Each species has, like the individual, a limited life, a 

 beginning and an end, and the end of the species is its breaking 

 up into new progressive forms. The zoologist Strandfuss uses 

 the expression -'explosion" with regard to the breaking up of the 

 species into new forms, as if the old species "explodes" into 

 numerous pieces, some of the pieces getting lost, while others 

 develop into new species. The old botanists use the astronomical 

 expression " Nebula " for extremely variable or " very much 

 exploded " species, such as Hieraciuiii, Ruhus, Rusa, Salix. 



An interesting problem for investigation is to find out the 

 species in which the mutation-period takes place at the present 

 day. Prof. De Vriese knows only one plant which fulfils all 

 necessary conditions, ?.e., Oenothevd Lamarckiana^ a species intro- 

 duced from America, and now slowly spreading in several 

 European countries for a period of about a centur}''. 0. Lamarck- 

 iana has the rare and remarkable property of producing every 

 year new species from seeds. The seeds of 0. Lamarckiana are 

 sown in sufficient quantities (care having been taken to avoid all 

 possibility of cross-fertilization with allied species); a number of 

 new species will always be found amongst the seedlings. Prof. 

 De Vriese enumerates 7 species thus obtained by him from 0. 

 Lamarckiana, without cross-fertilization. The species are : — 

 0. nanella, lata, scintilla7is, oblovc/a, albida, gifjas, and ruhrinervis. 

 These new species difier onl}' slightly from the mother plant, and 

 only close observation teaches that new forms have made their 

 appearance, but they are all quite distinct from each other and 

 perfectly stable from the beginning, so that seeds of 0. gigas 

 again produce 0. giyas. 



