Nos. 622-623] 



ORGANIC EVOLUTION 



52:: 



preted as arising from sudden and comparatively ex- 

 treme variations passed on by inheritance in nearly an 

 unchanged condition. Once more the results of experi- 

 mental work along the lines of the rediscovered principle 

 of Mendelian segregation indicated to a large number of 

 students of evolution that the facts set forth by DeVries 

 were subject to quite another explanation, in itself hav- 

 ing no bearing on the origin, but merely on the redistribu- 

 tion of the character-forming units already present in 

 the stock utilized. Another explanation not taking into 

 account the purity or impurity of the parental stock, ac- 

 counted for "mutations" through the sudden ineffective- 

 ness or loss of a gene. 



The dissatisfaction thus arising resulted in the return 

 of many to the fold of "acquired characters." Semon 

 (1912) reviving the "mneme" principle received the sup- 

 port of Wettstein, Przibram, and others. A disinclina- 

 tion existed, however, among most naturalists to accept 

 the evidence presented as seriously upholding the inheri- 

 tance of new characters produced by environmental 

 stimuli. Explanations of the results on quite other 

 grounds seemed more plausible. For example, the work 

 of Tower (1906), (1910), etc., in attempting to control the 

 color pattern of the potato beetle by changes in tempera- 

 ture and humidity, encountered the impurity of the germ- 

 plasm objection as well as the gene loss objection, either 

 one of which would be fatal to the validity of the conclu- 

 sions, if sustained. Commenced at a period in 1895, prior 

 to the rediscovery of the principles dealing with alterna- 

 tive inheritance, and finished in 1904 before the facts 

 w r ere duly appreciated, it is not at all improbable that 

 genetic complications in the way of recessives, modifiers, 

 losses, lethals, etc., were involved. The destructive criti- 

 cism presented by Cockerell, Gortner, Bateson, Castle, 

 and others, particularly in reference to the later studies 

 of Tower (1910), makes it evident that the results must 

 be confirmed from independent sources with more con- 

 sideration to the possible errors mentioned before the 

 conclusions are to be accepted. 



