64 POPULAR SCIENCE MONTHLY. 



with them that which nature herself seems unable to do, namely, to 

 dissociate them from the rest of the organization and perfect them in 

 this way or in that. It is this meddling with the fluctuating char- 

 acters of the species that has been the characteristic procedure of the 

 Darwinians, in their attempt to show how new species have been 

 created. In contrast to this method, the theory of the survival of 

 species assumes that a form once made does not have its individual 

 parts later disassociated and adjusted to better fit the external needs 

 of the species. Such a new form can change only by becoming again 

 a new species with a new combination of characters; some of which 

 may be more developed in one direction than before, others less ; etc. 



New forms on the Darwinian theory are supposed to be created by a 

 process of picking out of individual differences. If, in addition to this, 

 Darwin supposed that at times varieties and species crowd each other 

 out nothing new is thereby created.* On the other hand the theory of 

 the survival of definite variations refers the creation of new forms to 

 another process, namely, to a sudden change in the character of the 

 germ. The creating has already taken place before the question of 

 the survival of the new form comes up. After the new form has ap- 

 peared the question of its persistence will depend on whether it can 

 get a foothold. The result is now the same as when species crowd each 

 other out. This distinction appears to me to be not a matter of second- 

 ary interest, but one of fundamental importance, for it involves the 

 whole question of the ' origin of species.' So far as a phrase may sum 

 up the difference, it appears that new species are horn; they are not 

 made by Darwinian methods, and the theory of natural selection has 



*If the survival of certain species determines, in a metaphorical sense, 

 the kinds of future mutations that occur, the course of evolution may appear 

 to be guided by selection or survival; but however true it may be that selec- 

 tion acts by lopping off certain branches, and limits to this entent the kinds 

 of possible future mutations, the origin of the new forms remains still a 

 different question from the question of the survival of certain species. This 

 negative action of selection is not the process that most Darwinians have had 

 in mind as the source of the origin of new species. It is true that Weismann 

 believes that selection of individual differences determines the origin of new 

 species, and that the creation of these new species determines the future course 

 of variations in the same direction, but his argument that fluctuating varia- 

 tions can go on indefinitely varying in the direction of selection is refuted 

 by what has been actually found to be the case when the process of selection 

 of fluctuating variations is carried out. Most of the individuals of a species 

 may be brought in this way to show the particular character selected in its 

 highest degree as a fluctuating variation, but it appears not possible to trans- 

 gress this limit; and rigorous selection in every generation is necessary to 

 hold the individuals to the highest point reached. Only by the appearance 

 of new definite variations can a given character be permanently fixed, or a 

 new species created that will show fluctuating variations around the new 

 standard. 



