IV DORFMEISTER'S EXPERIMENTS 



131 



climate, so must the modification which is produced i'roni 

 the transformed species of our example after the return of 

 the first climate be different — though perhaps in a less 

 degree — from the original form of the species. In otlier 

 words, if in succeeding geological periods only two different 

 climates alternated on the earth, yet from every species of 

 butterfly subjected to this alternation would be derived an 

 endless series of different species. In reality the variety of 

 climates must have been much greater, and climatic changes 

 for a given species have taken place, not only throuyli 

 periodical variations of the ecliptic which may be assumed 

 to occur, but through geological transformations, and also 

 through migrations of the species itself. Thus from tliis 

 sincjle cause — variation of climate — a continual chan^'c of 

 species must have taken place. When we reflect that species 

 extinct elsewhere must have survived locally, and add to 

 these those local forms which owe their oricjin to amixis/ we 

 cease to be astonished at the enormous number of species of 

 Lepidoptera which w^e find on the earth at the present day." 



It is unnecessary for me specially to point out how dis- 

 tinctly the above passage, which so exactl}^ agrees with my 

 own views, implies the recognition of the inheritance of 

 acquired characters. 



Dorfmeister has, he tells us, ever since 1845 made experi- 

 ments on the effect of temperature on the colour and marking 

 of butterflies. He explains first of all that through many 

 years' experience in rearing caterpillars he has been convinced 

 that the production of varieties of butterflies depends mucli 

 more on climatic conditions, in which temperature is a chief 

 factor, than on either food or hybridisation. Dorfmeister learns 

 from his experiments that temperature exercises the greatest 

 influence on the colour and marking of butterflies when it 



1 Cessation of interbreeding. Pammixis^indiscrinuiiate interbreeding. 



