OTHER THEORIES OF SPECIES-FORMING. 211 



show a congenital variation bringing the leg muscle up to 

 eight cm. of thickness. Now if it requires a leg muscle of 

 eight cm. for safety, as a matter of fact almost all the indi- 

 viduals of the species will quickly bring their leg muscles up 

 to that size by use. But suppose the actual need for safety 

 was a leg muscle of fourteen cm., then only those individuals 

 specially capable of that cntogenetic adaptation, i. e. (modi- 

 fication of the leg muscle by use and trophic irritability), up 

 to fourteen cm., would be saved ; and undoubtedly among 

 these the original eight cm. individuals ought to stand in 

 slightly higher numerical proportion (in regard to their 

 original numerical standing in the species) than the origi- 

 nally seven cm. individuals. Since, however, these eight cm. 

 individuals originally existed only in comparatively small 

 number, and since they possess no special means of recognis- 

 ing each other and distinguishing each other from the 

 original seven cm. individuals, mixed mating will inevitably 

 soon swamp the original congenital increase of one cm. in 

 muscle thickness. 



In connection with the explanation of this theory it will 

 certainly occur to some of my readers, as it has to me, to ask 



Danger of if it: is not a dangerous proposal to give to 

 assuming too ontogenetic adaptations a greater worth in 

 ance ofonto- deciding the fate of individuals during the 

 genetic selection, struggle for existence than the congenital varia- 

 tions. Is this not proposing to take away from the fluctuat- 

 ing, individiual, so-called Darwinian variations practically 

 all worth and capacity except as they are of immediate use 

 to the just-born individuals, i. e., before the ontogenetic 

 adaptations have been able to develop ? Indeed, why is it not 

 a perfectly legitimate and a serious criticism of congenital 

 fluctuating variations that they must be overshadowed, hid- 

 den, and overwhelmed by the quick and large ontogenetic 

 or individual modification of which practically all organisms 

 are capable ? Why will not those individuals born with the 



