112 



SCIENCE. 



[N.S. Vol. XXII. No. 552. 



the mutative birth of one or more of her 

 progeny. 



Species thus produced by mutation are 

 called elementary species. They differ dis- 

 tinctly but not widely from the mother 

 species; wide differences result from the 

 absence of intermediate elementary species. 

 That is, the daughter species become 

 mother species successively; a large part 

 of the mutated, as well as of the ordinary, 

 offspring soon perish in the struggle for 

 existence, even with their own kindred, 

 until wide differences between species of 

 the same stock result. Species are de- 

 stroyed in the struggle for existence, but 

 that struggle plays no part in their origi- 

 nation. 



That species have a real entity and, for 

 the most part, an essentially unchanging 

 existence, are facts of daily observation. 

 They are born, and if they survive the 

 struggle for existence to which they are 

 immediately subjected, they usually have 

 an extended duration; but they finally 

 perish. The duration of a species has two 

 periods, a mutative and a non-mutative 

 period ; the former being exceedingly short 

 in comparison with the latter. So very 

 much is the non-mutative period of all 

 species in excess of the mutative, that all 

 the species living in any large region at 

 any given time are likely to be in the non- 

 mutative condition. Furthermore, the 

 process of mutation is so inconspicuous 

 that it may easily escape detection. At- 

 tention is particularly called to the fact 

 that mutation, using that term in its here 

 adopted special sense, is as much a natural 

 and normal process as is that of ordinary 

 reproduction, with which function every 

 case of mutation is concurrent. It is also 

 in no way opposed- to the great thesis of 

 evolution, and is in full accord with Dar- 

 win's theory of common descent. 



By referring to the three assumptions 



of the advocates of the theory of the origin 

 of species by natural selection which are 

 mentioned in the early part of this article, 

 and comparing them with the immediately 

 preceding statement of the mutation theory, 

 it will be seen that this theory is directly 

 opposed to them, but consistent with the 

 facts which have been stated in preceding 

 paragraphs. By further referring to those 

 statements it will appear that in all the 

 cases wherein the inapplicability of the 

 origin of species by natural selection has 

 been shown, the mutation theory is fully 

 applicable. Indeed, the applicability of 

 the latter theory is so apparent that only 

 the following brief comments will be made 

 in conclusion. 



The assumption of an inimitably remote 

 period for the beginning of life upon the 

 earth, which the theory of the origin of 

 species by natural selection requires, and 

 which has been vigorously opposed by 

 physicists as inconsistent with cosmical 

 law, is shown by the mutation theory to 

 be unnecessary. That question is, there- 

 fore, eliminated from all such discussions 

 because the mutation theory presupposes a 

 rapidity of evolution that would bring the 

 beginning of life quite within the limits 

 required by the physicists. 



The comparative rapidity of introduc- 

 tion and dispersion upon the earth of cer- 

 tain genera, families, orders, classes and 

 even of great faunas and floras, makes it 

 necessary to infer the sudden origin of 

 their elementary component units. Those 

 facts and the inference mentioned are as 

 consistent with the mutation theory as they 

 are inconsistent with the theory of the 

 origin of species by natural selection. Fur- 

 thermore, the persistence of those faunal 

 and floral groups through long periods of 

 geological time with little change after 

 they had become established, makes it 

 necessary to infer the stable entity and 



