Page:Popular Science Monthly Volume 69.djvu/212

208 generation, eliminating guesswork as to parentage, and prophecy as to offspring. The first is steadily yielding results of undoubted importance and is bringing about a renewed interest in the functional relations of the components of the protoplast with respect to the inheritance of characters. The second method, that of statistical observations and experimental methods in pedigreed cultures, has given such notable results in the hands of various investigators, that it may be truly asserted that it may not be outclassed in value by any form of research yet used in investigations in natural history.

As an explorer, do you wish to ascertain the source, direction, character, rate of flow and confluence of a river across your route? Surely, you do not reasonably attempt it by an examination of a single reach, or from a photograph of a single waterfall. Even so surely you may not gauge the possibilities of development, or estimate the potentiality or method of action of groups of characters, embraced in a hereditary strain, guided by dimly recognized forces for thousands of years, by the measurement of a preserved specimen. Physiological problems demand analytic methods of observation of living material.

What ridicule might we not heap upon a botanist who attempted to make a study of geotropism from consideration of the dried material in a herbarium. The existence of such a form of reaction might indeed be recognized, but what futile inferences might be drawn as to its mechanism or the nature of the results. It seems unnecessary and superfluous to call attention to a generalization so obvious; yet that the necessity is not lacking is shown by the material that crowds the pages of our technical magazines and popular periodicals.

Before proceeding with the main thesis it will be profitable to notice some of the most glaring of the inadequacies of treatment which have been recently exhibited, and to call attention to certain unsupported statements which so far have gone unchallenged.

A vice-president of the American Association for the Advancement of Science, in a recent address, has taken occasion to call up the mutation theory, and assumes to have given it a test by "reexamining certain groups of birds and mammals, of which I had previously made systematic studies, for the purpose of discovering evidence, if such exists, of the formation of species by mutation." This author says that "for a quarter of a century I have been an earnest field student of plants in relation to geographic environment. These studies have convinced me that with plants as with animals the usual way in which new forms (subspecies and species) are produced is by gradual progressive development of minute variations." In regard to this comprehensive statement I may say that I have read practically every