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THE AMERICAN NATURALIST 



[Vol. XLVI 



instinct we are all Lamarckians and are inclined to fol- 

 low Darwin in ascribing variability of every sort, germi- 

 nal as well as somatic, to changed conditions of life. But 

 this is by no means a necessary conclusion. It is con- 

 ceivable that germinal variations result from combina- 

 tions of different germplasms, as Weismann supposed, 

 that the determiners of Mendelian characters do not 

 always preserve their individuality, but sometimes unite 

 in such way as to modify the unit characters ; but as yet 

 we have no evidence that new characters are formed in 

 this way, and the study of Mendelian inheritance has 

 made this possibility less probable than it once was. 

 Again it is possible that germinal variations, and new 

 hereditary characters, may result from intrinsic changes 

 in the germplasm, comparable to the spontaneous changes 

 which occur in radium, for instance; such a view of 

 transmutation through intrinsic, spontaneous, changes 

 has points of resemblance to the doctrine of orthogenesis, 

 but of its truth or falsity we have no sufficient evidence. 



If changes in the germplasm may be induced by ex- 

 trinsic conditions, then a real experimental evolution will 

 be possible ; if they can not be so induced we can only look 

 on while the evolutionary processes proceed, selecting 

 here and there a product which nature gives us, but 

 unable to initiate or control these processes. 



Ill 



Darwin's theory that selection is the most important 

 factor in preserving and building up evolutionary char- 

 acters remains to this day a theory. The brilliant re- 

 searches of our distinguished guest, Professor Johann- 

 sen, and of our President, Professor Jennings, have 

 shown that the selection of fluctuations, or somatic varia- 

 tions, have no permanent effect in modifying a race ; but 

 selection or elimination of germinal variations may be 

 an important factor in evolution, though it has little or 

 nothing to do with the formation of new characters, and 

 serves merely as a sieve, as De Vries has expressed it, to 

 sort the characters which are supplied to it. 



