2 2o POPULAR SCIENCE MONTHLY. 



tion of species. He, too has not yet succeeded in analyzing and dis- 

 tinguishing from each other — what has been de Vries's merit — varia- 

 bility within the boundaries of constant species and mutability which 

 does not fluctuate, but which by a sudden bound leads to the new 

 species. 



Much closer to this valuable discovery we find two students of the 

 fossil-animal kingdom, two paleontologists, one of whom (Waagen), 

 as long as twenty-five years ago, understood the importance of the 

 phenomenon of mutation, even without the support which the series 

 of de Vries's experiments would, of course, have afforded him, while 

 the second (W. B. Scott, of Princeton) has most clearly expressed him- 

 self (American Journal of Science, 1894) that the formation of species 

 by selection of fluctuating mutations, such as Wallace maintains, is 

 rendered most improbable by what the fossil-animal world teaches us. 



This world of fossil animals exhibits in certain regions of the earth, 

 where the successive geological formations have been retained in un- 

 disturbed order, a similarly undisturbed ascending series. Far from 

 finding in that series the divergent fluctuations which Bateson had 

 accepted for so many animals, Scott has shown (and has strengthened 

 his argument by referring to the results of many other paleontologists) 

 that these fluctuations are indeed — though exceptionally — found among 

 fossil animals as so many individual deviations (thus proving that 

 also in that time the fluctuating variability existed within the limits 

 of the species) — but he is at the same time convinced that this phe- 

 nomenon has nothing to do with the slow modification of species, 

 which takes a straight line and not a zigzag one. 



Scott, although he was not at that time acquainted with de Vries's 

 experimental evidence, staunchly holds to the idea that species have 

 not grown out of the gradual selection of deviating individuals, but 

 have appeared by mutation, by very small but sudden starts from one 

 stage to the next. 



We see before our eyes how the species of the deeper layers are 

 gradually modified as we reach the higher layers; we find that all in- 

 dividuals simultaneously underwent this modification; in other terms, 

 the phenomenon can hardly be described otherwise than by saying 

 that the older species tends directly towards an aim, which the younger 

 species that has descended from it has attained. 



Many paleontologists even go so far as to admit a previously de- 

 termined direction in gradual evolution. There is, of course, close 

 affinity between such a predetermined direction in evolution and the 

 teleological idea of design presiding at the creation of species. Clerical 

 opponents of evolution may here have their chance of adapting the 

 newest results in the study of that process to their personal principles. 



