38 SPOLIA ZEYLANICA. 
one’s mind, which unconsciously causes one to describe things 
in its own terms. There is, for instance, a general tendency 
among naturalists to make every peculiarity of living things 
fali in line with the theory of natural selection, and when such 
and such an animal or plant is found to possess such and such 
a puzzling feature, then we immediately invent a use for the 
said puzzling featura, and declare that its use is the cause of 
its existence. When we cannot invent a use, we assume that 
it once had one, and call it rudimentary, or that its full fune- 
tion is yet to be, and say the feature is elementary. Failing 
these, we say we have not discovered its use, but we firmly 
believe that sooner or later we shall find a use for it. In 
adopting this position we fail to realize the unwarrantable 
nature of the assumption we make in doing so, 7.e., that every- 
thing that survives in Nature has some selective value. Again, 
if any organ can be shown to have a use, we never fail to assume 
that that organ has played a very significant part in the 
evolution of its possessor, and this on account of a pre- 
conceived idea of what evolution means. 
Theory, you will observe, is guiding description. The 
temptation to read one’s pet ideas into Nature has always 
been a great failing with the naturalist, and is probably no 
less common to-day than it was centuries ago. It is this 
process of ‘‘ reading in” which has been dignified by the name 
of reasoning from analogy—a title which it unquestionably 
deserves, for, whereas the common sense interpretation of 
Natur: depends upon the /ikeness of things, the scientific con- 
ception is founded on differences. For example, the sameness 
of the signs of life as exhibited in both the plant and animal 
kingdoms has lead to the idea that any general principle in the 
one will be found to have its equivalent in the other. Conse- 
quently, it was thought that the phenomenon of circulation 
as seen in the arterial and venal systems of animals was to be 
paralleled by the passage of the sap in the xylem and phloem 
tissues of plants, and when Mr. Ruskin (after turning up all 
the indexes of the best botanical authorities of his day) found 
occasion to grumble at those gentlemen because he could 
find no reference to the “ circulation of the sap,” he had to be 
told that the botanists had discovered their mistake. _ 
