384 THE POPULAR SCIENCE MONTHLY 



philosophy. When presented with Darwin's conception of evolution, 

 the botanist and zoologist could no longer remain satisfied with mere 

 contemplation of privileged moments. It became necessaiy to attend 

 to every aspect of the organism. Every phase of its development from 

 the egg to its dissolution, and every particle of its structure had to be 

 submitted to the closest examination, for no character — so ran the 

 theory — was too insignificant to decide whether a species could survive 

 in the struggle for existence. Indeed, even vestigial and rudimental 

 characters began to assume an astonishing importance as witnessing to 

 the past and prefiguring the future history of the species. Such close 

 scrutiny of the entire life-cycle and structure of organisms was also 

 necessitated by Darwin's assumption that the evolution of organic forms 

 is a very gradual process, requiring enormous periods of time. Hence 

 the incentive to record the minutest variations and adaptations and to 

 search for their causes. From the same source sprang the inspiration 

 to study the lower animals and plants with the utmost care and in all 

 their aspects, for these forms — according to the theory — had departed 

 least from the first, simple beginnings of life on our planet, and might, 

 therefore, be expected to throw light on the initial movements of 

 organic evolution. But the animals at the other end of the organic 

 scale were not to be neglected, for the theory which made man a blood 

 relation of the higher mammals could not fail to arouse universal 

 interest in these and all the other vertebrates. And not only did it 

 become necessary to investigate the plants and animals now living on 

 the earth, but the strata of the planet had to be ransacked for evidences 

 of past evolutionary history. Paleontology was born anew, and the dis- 

 tribution of life in the present and past became a subject of absorbing 

 and ardent study. Even the most conservative branch of biology, the 

 classification of animals and plants, was shaken to its foundations by the 

 theory of evolution, for under its solvent action the old conceptions of 

 the genus and species, and all the other taxonomic categories, lost their 

 rigid outlines and became fluid and dynamic. In proof of all these 

 statements concerning the immediate effects of the promulgation of the 

 theory of evolution, we have only to glance at the marvelous develop- 

 ment during the past fifty years of anatomy, embryology, histology, 

 cytology and physiology, both human and comparative, and of paleon- 

 tology, chorology, ethology and taxonomy, both botanical and zoological. 

 The constantly increasing tendency during the past half century to 

 substitute a careful genetic study, that is, a study of all the stages 

 of the life-processes, with a view to establishing the laws or constants 

 of their occurrence, for the ancient cut and dried methods of defining 

 and classifying concepts obtained from the contemplation of privileged 

 moments in the vital flux, has spread far beyond the confines of biology 

 properly so-called. Psychology, which is the most closely related of all 



