PRESIDENTIAL ADDRESS. 25^ 



tion that the causal nexus is in any sense adequately known. 

 Still, for myself, I prefer it to the " fortuitous " phraseology. 

 The analog}^, and it is at best a distant one, is with " laws of 

 crystallization." We know that under different conditions 

 the same chemical substance will crystallize as either calcitr. 

 or aragonite^ another as either hornblende or augite, another 

 as either 7narcasite or iron pyrites. It is part of the in- 

 herent nature of the substance in each case : we cannot at 

 present say much more than that. Similarly determinate 

 variations, under different environing conditions, or under 

 special combinations of characters, may be the outcome of 

 the inherent nature of the organism concerned. That is 

 probably the utmost we can say at present. Of course 

 those who wholly disbelieve in determinate variations will 

 murmur " moonshine." Let them prove their case. Let 

 them show that the apparently determinate variations are 

 not really such, or if they are such that they result from 

 selection from among indeterminate variations. And let 

 them explain the origin of new characters.. If they are 

 successful, I shall be one of the first to congratulate them. 

 I am not wedded to any opinion. All I contend for is free- 

 dom of discussion and further observation. In effect the 

 question, so far as we have got at present, is between 

 "determinate variation under laws of organization," and 

 " indeterminate change under a law of inherent variation." 



We now come to the vexed question of use-inheritance, a 

 convenient term coined by Mr. Piatt Ball to express the 

 transmission from parent to offspring of characters not 

 innate in, but acquired during the lifetime of, the parent. 



In evidence of this transmission of the effects of use and 

 disuse, Mr. Herbert Spencer has adduced the diminution of 

 the jaws in civilized races of man, the diminished biting 

 muscles in lap-dogs, the development of the sesthetic 



