Page:Popular Science Monthly Volume 45.djvu/194

180 must be enormously increased with the development of every species. A new principle must therefore be found to explain the observed fact. Strangely enough, he finds this principle to be none other than the Lamarckian law of the effect of external conditions in modifying the hereditary elements!

"Amphimixis alone could never produce a multiplication of the determinants. The cause of hereditary variation must lie deeper than this; it must he due to the direct effect of external influences on the biophors and determinants."

It is easy to see that this is a complete abandonment of his fundamental doctrine of the immutability of the germ-plasm, and here again he shifts the point of the argument to the quantitative* and would have us believe that it was the same thing to say that it possesses "great power of remaining constant." But he adds:

"We can none the less avoid assuming that the elements of the germ-plasm—i.e., the biophors and determinants—are subject to continual changes of composition during their almost uninterrupted growth, and that these very minute fluctuations, which are imperceptible to us, are the primary cause of the greater deviations in the determinants, which we finally observe in the form of individual variations."

These variations that take place in the hereditary elements he ascribes to "the impossibility of a complete uniformity as regards nutrition existing during growth," or to "the modifying influence of nutrition." The following passage is as complete an admission of the Lamarckian principle as any one need wish, while at the same time it illustrates over again his characteristic tendency to evade the issue by maintaining that its influence is small compared to that of some other principle:

"Even though it can no longer be doubted that climatic and other external influences are capable of producing permanent variations in a species, owing to the fact that, after acting uniformly for a long period, they cause the first slight modifications of certain determinants to increase, and gradually affect the less changeable variants of the determinants also, the countless majority of modifications is not due to this cause, but to the processes of selection."

In this passage there is a curious psychological implication in the expresssion "no longer," which obviously refers to the changes in his own mind, that are by him projected to the world at large, which, as a matter of fact, has from the first intuitively arrived at the conclusion which has cost him such a great cycle of elaborate reasoning. This new theory of his as to the origin of variations is summed up in the following paragraph: