go NATURAL SCIENCE. Feb., 



question whether these effects are inherently adaptive. Lyell was 

 ignorant of the principle of selection when he wrote the first edition 

 of the "Principles" ; but to us, who know the value of this adaptive 

 mechanism, the question narrows down to the evidence that the 

 "Lamarckian factors" can give rise to even "the incipient stages of 

 adaptive modification." 



As the strengthening of muscles by exercise is one of the simplest 

 examples of the beneficial effect of the conditions of life, we may find 

 instruction in its attentive consideration. In the strict sense of the 

 words, it is not use, but increase in the food-supply, which enlarges 

 the muscle, and this increase may be brought about by massage or 

 by electrical stimulation as well as by exercise. Contractions and 

 relaxations of the muscle increase the supply of food, because the 

 muscle is so constructed that the nutritive fluids are drawn through it, 

 in the right direction, by its normal contractions. The improvement 

 of the muscle by exercise is the effect of a structural adjustment for 

 securing this useful end — it is an adaptation ; and the muscle is as 

 obviously, if not as definitely, adapted for improvement by use as the 

 heart is adapted for propelling blood. Exercise increases its efficiency 

 only so far as structural adjustments for bringing this about already 

 exist, and the real problem, the origin of the adaptation, is in no way 

 different from that presented by any other structural adaptation. 



This is still farther illustrated by the fact that organs are im- 

 proved only by normal or natural use, while abnormal or unnatural 

 use is well called abuse, as contrasted with use. It is only when our 

 organs are used in that way which is popularly described as " the 

 way they were intended to be used," that use is beneficial. 



Romanes tells us, p. 59 : " Inasmuch as we know to what a 

 wonderful extent adaptive modifications are secured, during individual 

 lifetime, by the direct action of the environment on the one hand, and 

 by increased or diminished use of special organs and mental faculties 

 on the other, it becomes obvious of what importance even a small 

 measure of transmissibility on their part would be in furnishing to 

 natural selection ready made variations in required directions, as 

 distinguished from promiscuous variations in all directions. Con- 

 trariwise, if functionally produced adaptations and adaptations by the 

 direct action of the environment are never transmitted in any degree 

 . . . there would be an incalculable waste, so to speak, of adaptive 

 modifications." 



This argument has seemed, to many persons, a plausible one, but 

 it is clear that it involves a most serious fallac}^ unless the inheritance 

 of the effect of the " Lamarckian principles " can be proved to be 

 selective ; for the ways to use a muscle are few, while the ways to 

 abuse it are innumerable, and the inheritance of all the effects of the 

 conditions of life must lead, not to " cumulative adaptation," but to 

 cumulative destruction. Unless these factors can be shown to have, 

 antecedently to selection, a determinate influence in beneficial lines, 



