322 Difficulties of Darwinism. [July, 
as a warning to mathematicians who persist in rearing up 
imposing superstructures upon imaginary data. That the 
respective distribution of land and sea in the two hemi- 
spheres may have fluctuated greatly from changes in the 
earth’s centre of gravity, and that partial and even extensive 
deluges may have occurred, is a perfectly reasonable 
supposition. 
V. DIFFICULTIES OF “DARWINISM.” 
UCH of the unprofitable ink-shed by which the so- 
called ‘‘ Darwinian controversy ” has been obscured 
has sprung from the neglect of a very plain dis- 
tinction. Evolution—the gradual mutation of organic 
forms in accordance with definite laws, and the consequent 
origin of what we call ‘‘ species ’”’—may be a fact, as the 
writer is by no means disposed to question. But its truth 
does not necessarily involve the truth of the doftrine com- 
monly known as “ Natural Selection.” It may yet be 
shown that this theory, supplemented by Sexual Selection, 
will account for all the unsolved mysteries of the organic 
world. Or it may—and probably will—be found that we 
require the aid of some law of a higher order, defining the 
limits and the conditions under which the great task of Evo- 
lution is carried out. Or, lastly, it is byno means impossible 
that the entire theory of Natural SeleCtion may have to be 
thrown aside. Its future depends simply on its power of 
explaining facts. So long and so far as it is able to do this, 
it is our duty to follow it. But if we find it fail us, we must 
be prepared either to supplement it with some more efficient 
conception or to abandon it altogether. It is with a view of 
testing this theory that the following nuces zoologice are sub- 
mitted to the world. The writer does not hold that they 
can be more fully solved on the hypothesis of distinct and 
special creation than that of Evolution. But the reverse 
ought to hold good. Unless a new dodtrine does us better 
service than the old one, how is it to be legitimated ? 
Let us first examine the colouration of animals, and con- 
sider in how far it can be accounted for by Natural Selection 
supplemented by Sexual Selection. In the Mammalia the 
first point which strikes us is the very limited range of 
colour which they possess. We question if a single instance 
