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 characters 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.[1] 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 appeared 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 secondary 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 born; 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 selection 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 variations 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 transgress 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.
