THE SYNTHETIC PHILOSOPHY: ITS THEORY OF EVOLUTION. 567 
_ required numerous and wide-spread modifications.”” Mr. Spencer illustrates this 
fact quite fully, showing that to establish any such modifications of a part involves 
a modification of the whole organism, which, at best, he concludes, is necessari- 
ly a slow process and one requiring great time for its accomplishment. 
Concerning the limit to which such modifications may be extended, he says: 
«<The general truth, that extra functions are followed by extra growth, must be 
supplemented by the equally general truth, that beyond a limit, usually soon 
reached, very little, if any, further modification can be produced. The experi- 
ences from which we draw the one induction, thrust the other upon us.” After 
somewhat fully illustrating this truth he proceeds: ‘‘ Thus the general fact appears 
to be, that while in each individual certain changes in the proportion of parts may 
be caused by the variation of functions, the congenital structure of each individ- 
ual puts a limit to the modifiability of every part. Nor is this true in individuals 
only ; it holds in a sense, of the species. Leaving open the question, whether 
in indefinite time, indefinite modifications may not be produced, experience 
proves that within assigned times, the changes wrought in races of organisms by 
changes of condition fall within narrow limits.” In view of the great difficulty 
of affecting such modifications at all and in the long time required at best; and in 
view of the fact that they are limited to the congenital structure of the individual, 
and in view of the fact that the same holds true of species, it seems necessary to 
think that the type of the race cannot change, hence that there cannot be evolu- 
tion; for if the modifiability of both species and individuals is limited within the 
congenital structure of the individual, it is impossible to conceive how that con- 
genital structure, which is the type of the race, can become changed. 
Yet, that there may be and are, variations within the limits of the type of any 
race of organisms, is a fact patent to common observation and recognized by 
science. Mr. Spencer thus refers to it: ‘‘ It seems that in each species of organ- 
isms there is a margin for functional oscilations on all sides of a mean state, and 
a consequent margin for structural variations; that it is possible rapidly to push 
functional and structural changes toward the extreme of this margin in any direc- 
tion, both in an individual and ina race; but that to push these changes farther 
in any direction and so alter the organism as to bring its mean state up to the 
extreme of the margin in that direction, is a comparatively slow process. 
Change of type, then, could result only from so pushing an individual organ- 
ism up to this limit, and pushing those of its offspring beyond. The facts of 
heredity will illustrate the feasibility of this. In treating of heredity, Mr. Spencer 
states these facts: ‘‘First in order of importance comes the fact that not only 
are there uniformly transmitted, from an organism to its offspring, those traits of 
structure which distinguish the class, order, genus and species, but also those 
which distinguish the variety. We have numerous cases among both plants and 
animals, where, by natural or artificial conditions, there have been produced 
divergent modifications of the same species, and abundant proof exists that the 
members of any sub-species, habitually transmit their distinctive peculiarities to 
IV—3s 
