2 3 o POPULAR SCIENCE MONTHLY. 



though seen only in minute features, may always be recognized again. 

 These varieties in time Waagen termed mutations. In 1891 Scott un- 

 earthed this distinction of Waagen's and clearly defined it as the hered- 

 itary or phylogenetic change of animals in time. Previous to this 

 Osborn, without knowing of Waagen's statement, had discussed the 

 same facts of the birth of new characters, describing them as ' definite 

 variations.' Cope, it happens, did not follow this line of thought at 

 all; but many other paleontologists did, notably Hyatt, whose peculiar 

 style and multiplicity of terms obscured his depth of thought and 

 extent of observation. Thus the term mutation acquired a definite 

 significance among paleontologists. 



It happened that De Vries, the eminent Dutch botanist, reading 

 Scott's paper, mistakenly identified these new characters succeeding 

 each other in time with those which he was observing as occurring con- 

 temporaneously in plants, and he adopted Waagen's term for the 

 ' mutation theory,' which he has so brilliantly set forth, of the sudden 

 production of new and stable varieties, from which nature proceeds to 

 select those which are fit. 



If paleontologists are correct in their observation, mutations may 

 be figured graphically as an inclined plane, whereas De Vries's phe- 

 nomena in plants represent a series of steps more or less extensive. 

 Scott expressly excluded the element of discontinuity; and I believe 



I there is no ground whatever for the assertion that the'pnenomena first 

 named mutations by Waagen and independently observed by many 

 paleontologists, are identical with the phenomena observed by De 

 ,: Vries in plants. 



On the contrary, De Vries's facts accord with the favorite hypothesis 

 of St. Hilaire. They demonstrate the law of saltation. This is the 

 inevitable interpretation of the expositions of De Vries himself, of 

 Hubrecht, and of the more recent references of Bateson in his British 



^ Association address. That saltation is a constant phenomenon in 

 nature, a vera causa of evolution, no one can longer deny. Bateson 

 shows that it harmonizes with Mendel's conceptions of heredity, and it 

 may be regarded as par excellence the contribution of the experimental 

 method. 



Similarly, I regard mutation as a quite distinct phenomenon, and as 

 par excellence the contribution of the paleontological method; it is 

 the gradual rise of new adaptive characters neither by the selection of 

 accidental variations nor by saltation, but by origin in an obscure and 

 almost invisible form, followed by "direct increase and development in 

 successive generations until a stage of actual usefulness is reached, 

 where perhaps selection may begin to operate. While clearly setting 

 forth the difficulties, I at one time attributed definite variation or muta- 

 tion to Lamarck's principle of the inherited effects of habit as the 



