Problems of Heterogeneity 191 



not at present worth consideration, and the attributing of changes to the play 

 between internal parts after all only changes the scenery and not the nature of 

 the play. That is, it is interaction between the something which conditions the 

 character and the materials or forces, or both, external to itself at the point and 

 moment of reaction. 



It matters little at present whether I speak of the germ as a whole or of the 

 hypothetical lesser parts; whichever is chosen, the fimdamental operation in 

 transmutation is the interaction of the constitution of the gametic substance with 

 the conditions under which its activities go on. Two series of events are ever 

 passing — the antecedent genetic sequence of events in the material composition 

 of the gametes and the sequence of events in its medium ; at any moment the 

 constitution of the germinal material and its resultant soma are the product of 

 the dynamic interactions of the two. The two series of events in all instances 

 must be the prime factors in all transmutation phenomena, and they alone are 

 responsible for all transmutative changes of specific properties in organism. If 

 the two series of events are constant, there will be constancy of the resulting 

 organisms ; if the organism be plastic in its mechanism and adjusts itself easily 

 to divergent conditions, constancy with considerable adjustive oscillation will 

 result ; but if the organic mechanism be little or not at all plastic, divergence in 

 the conditions of its medium will result in adjustments between the mechanism 

 and its medium with change in the mechanism — a transmutative change. 



Eegardless of what future advances may bring us, the dynamic conception of 

 transmutation provides an easily applied working hypothesis of the cause of 

 change and one that is best expressed at present, though imperfectly, in terms 

 of physical science. 



ANALYSIS OF HETEROGENEITY. 



One of the most decided advances of recent years is the unquestioned demon- 

 stration that any real analysis of the heterogeneity and any expectation of under- 

 standing these phenomena must rest upon exact experimental methods of investi- 

 gation. Biometric analyses, descriptions of phenotypes, have their place as 

 methods of preliminary calibration of materials, but further knowledge depends 

 exclusively upon experimental analysis. Experimental analysis, however, is apt 

 to be pointless unless the results can be directly applied to the understanding 

 and investigation of conditions in nature. Obviously it is neither possible nor 

 profitable to consider all the characters presented, and the results obtained from 

 a few studies will be presented, as illustrating principles common to all specific 

 properties and attributes of organisms. 



In the study of heterogeneity of these qualities or specific characters I shall 

 begin with the simplest that I have been able to discover. ' These, while always 

 parts of a system, are specific in position, form, relations, etc. The differences 

 are often minute and would not ordinarily be used as " specific differences " by 

 taxonomists; however, in all respects they are distinct in character and alter- 

 native in behavior in crosses. 



