ACQUIRED CHARACTERS 33 



environment. It is doubtul whether any inheritance oc- 

 curred at all, for these animals usually reproduce by fission 

 and Ferroniere's " several generations " probably represent 

 merely regenerated fragments of one and the same original 

 individual. Had the transfer back to fresh water been gradual 

 enough there can be httle doubt that it would have been 

 accomplished successfully. 



(b) To a shorter season. Corn or other grain taken from a 

 southern to a northern latitude adapts itself to a shorter 

 growing season, maturing earlier. The change is not imme- 

 diate, but progressive, the period required for maturity grow- 

 ing shorter through several generations. This at first sight 

 looks like a good Lamarckian effect, but selectionists regard 

 it as equally good evidence in support of their view. For it 

 is evident that the shorter growing season in northern lati- 

 tudes would act as a selecting agency, killing off all variations 

 requiring a long growing season, so that earlier maturity 

 would become a racial character. 



5. Effects of changed food supply. Kellogg and Bell (1903) 

 fed larvae of the silkmoth on a reduced quantity of mul- 

 berry leaves or on a diet partly of lettuce, partly of mulberry 

 leaves. A decrease in size of the adult moths resulted which 

 persisted through two subsequent generations, even when 

 normally fed. In this way a race of dwarf moths was pro- 

 duced which however died out at the end of three genera- 

 tions. This is not a clear case of inherited modification, but 

 of direct weakening of the organism through mal-nutrition or 

 disease, the cause whatever it was being probably transmitted 

 in the egg like "pebrine." 



Similar but more extensive experiments were performed 

 by Pictet (1910-1911) upon larvae of the gipsy rmpth. These 

 larvae feed by preference on oak leaves. Pictet fed some on 

 walnut leaves and thus obtained moths of modified, paler 

 coloration. These modifications became accentuated after 

 several generations had been reared on walnut leaves. In 

 one experiment the modified coloration persisted in spite of 

 a return to normal diet. The first generation was fed on 



