1887.] 1-" [Claypole. 



VII. 

 A Possible Objection Considered. 



It ■will not improbably be objected that in thus attributing organic vari- 

 ation entirely to outward agency I am going considerably bej^ond what 

 can be proved. In the strict sense of the terra this is true. We cannot 

 yet demonstrate all the effects of physical change on a variable organism. 

 But we are constantly seeing more and more clearly the immense effects 

 of physical nature on organic beings. And experiments, purposed and 

 accidental, are gradually enabling us to trace special organic changes to 

 their causes in inorganic nature, and thus, as it were, to correlate the 

 kingdoms. A vast field of experiment lies here before us in the attempt 

 not merely to correlate but to commeasure these two, not only to deter- 

 mine what physical changes produce certain organic effects, but to measure 

 both, to estimate and weigh them and at length to predict the organic 

 effect of any given physical cause. 



And in this direction modern biological research is tending. The re- 

 sults already obtained warrant the hope that some day the present chaos 

 will be reduced to order, and the changes of organic nature will appear as 

 only the outcome of contemporaneous or antecedent changes in the physi- 

 cal world. A correlative and commensurate scale will be established. 

 Rest in inorganic nature, if possible, will be accompanied with iuvariauce 

 of organic nati;re, for as said above, no " tendency to vary " exists. On 

 the other hand change in the former, if uncompensated, must as certainly 

 induce change in the latter. The induction is not complete, as no induc- 

 tion ever can be, but the number of instances is already so great and so 

 rapidly increasing that the conclusion cannot be called premature, and 

 while every day increases its probability. 



It is true that we cannot as yet show many examples of invariance 

 through very long periods of time. Species die out and others come in. 

 Change is the rule, and we have so far found few exceptions. But the 

 biologist does not stand alone in thus advancing a step beyond the cover of 

 "bald facts." Other students in other departments are accustomed to do 

 the same, and boldly to accept the logical outcome of their observations 

 even in cases where for want of opportunity the crucial experiment can- 

 not be performed. A mechanical illustration will make the meaning 

 clear. The first law of motion is thus expressed by mechanicians: "A 

 body continues in a state of rest or of uniform rectilinear motion unless 

 acted on by some outside force. ' ' Yet the mechanician has never seen 

 "a body in a state of rest or of uniform rectilinear motion." His faith is 

 nevertheless unshaken. He argues that as every approximation to the 

 necessary conditions is followed by a nearer approach to such motion if he 

 could obtain perfect conditions, perfectly uniform rectilinear motion 

 would result. The force and justice of his argument are admitted. And 

 on proof like this he builds his science of mechanics, and on this science 

 the works of the engineer confidently rest. 



PKOC. AMER. PHILOS. SOC. XXIV. 125. Q. PRINTED MAY 21, 1887. 



