208 POPULAR SCIENCE MONTHLY 



generation, eliminating guesswork as to parentage, and prophecy as 

 to offspring. The first is steadily yielding results of undoubted im- 

 portance 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 ma- 

 terial 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. 



Inadequate Treatment of the Subject 

 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 unsup- 

 ported 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 pro- 

 gressive development of minute variations." In regard to this com- 

 prehensive statement I may say that I have read practically every- 



