362 THE EVOLUTION THEORY 



species must have settled in it from time to time, and the conditions 

 of life must have changed, and in many cases this must have led 

 to the extermination of species, in the same way, though not so 

 quickly, as human interference now brings about their doom. 



This is true for plants as for animals. A good example, not 

 indeed of complete extermination, but of very considerable diminution 

 in the numbers of individuals of a plant-species by the advent of 

 a species of mammal, is communicated to us by Chun in regard 

 to Kerguelen Land. A Howering plant, the Kerguelen cabbage 

 (Pringlea anttscorhuUca), has been greatly reduced in numbers since 

 the thoughtless introduction of rabbits to this uninhabited island 

 (1874). While, in i(S40, Captain Ross used this plant in great 

 quantities as a preventative against scurvy in his crew, and even 

 carried away stores to last for months, the Valdivia Expedition in 

 1898 found rabbits in abundance, ■ but the Kerguelen cabbage had 

 been entirely exterminated at ever}^ spot accessible to these prolific 

 and voracious rodents. It was only found growing upon perpendicular 

 cliffs or upon the islands lying out in the fiords. 



An avoidance of the threatened destruction of a species by 

 its adaptation to the new circumstances can only be possible when the 

 changes occur very slowly, and will therefore be more likely to 

 be achieved in the case of physical changes in the conditions of 

 life, such as climatic changes, a change in the mutual relations of land 

 and sea, and so on. But it appears that even climatic changes do not 

 evoke any variation and new adaptation as long as the species can 

 avoid the changes by migrating. The often quoted case of Alpine 

 and Arctic plants proves this at any rate, that those species which 

 inhabited the plateaus and highlands of Europe did not all vary 

 to suit the change when a warmer climate prevailed, but that in 

 part at least they followed the climate to which they were already 

 adapted, that is, that they migrated towards the north on the one 

 hand and higher up the Alps on the other. It cannot be denied 

 that many of the insects and plants did adapt themselves at that time 

 to the warmer climate, and became the modern species which now 

 inhabit the plains, for many related species occur on the Alps and in 

 the plains, but apparently many others simply made their escape from 

 a climate which no longer suited their requirements. Thus, as far 

 as I am aware, there is no species of Frimula in South or Central 

 Germany which could be derived from the beautiful red Primula 

 farinosa of the Alps, but this species occurs also upon the old 

 glacier-soil at the northern base of the Alps, and in similar soil 

 again in the north of Germany and on the meadows of Holstein. 



