THE FIXITY OF SPECIES. 63 
shifting the ground from one field of observation to 
another to make this statement, and when the assertions 
go so far as to exclude from the domain of science those 
who will not be dragged into this mire of mere assertion, 
then it is time to protest.” 
Dr. J. B. Warren, writing in a Presbyterian organ, 
more recently said: “If the theory of evolution be true, 
during the many thousands of years covered in whole or 
in part by present human knowledge, there would cer- 
tainly be known at least a few instances, or at least one 
instance, of the evolution of one species from another. 
No such instance is known. Abstract arguments sound 
learned and appear imposing, so that many are deceived 
by them. But in this matter we remove the question from 
the abstract to the concrete. We are told that facts war- 
rant the evolutionary theory. But do they? Where is 
one single fact?” 
The hypothesis assumes that through environment, 
certain varieties of species (both of plants and animals) 
arose, and that the varieties best fitted, through their 
habits, structure, or color, to maintain themselves in the 
struggle for existence, survived the species less favorably 
endowed, and hence persisted. (We have quoted in our 
initial chapter the classical illustration of the dipper- 
birds from Wallace’s “Darwinism.” ) 
Now, as a matter of fact, we cannot prove that a 
single species has changed. These are the words of 
Darwin himself, quoted from “Life and Letters,’ Vol. 
III, p..25: “There are two or three million of species 
on earth, sufficient field, one might think, for observa- 
tion. But it must be said to-day that in spite of all the 
efforts of trained observers, not one change of a species 
into another is on record.”’ Dr. N. S. Shaler, Professor 
of Geology in Harvard, asserts that “it has not been 
