s conclusions, says: "Since
Darwin we have been accustomed to consider the concept 'species' as
something insecure and unstable. The whole organic world must be thought
of as fluid if the evolution theory is to find room for action. It
required, indeed, all the great investigator's keenness to fence his
theory against the difficulty which the lack of transitional forms
occasioned, and against the fact that the rise of a new species has
never been observed, much more against the fact that all processes in
artificial breeding have not sufficed to fix permanently the changes
which have been attained. We admire the clever structure of the theory,
but there is no doubt that the obstinacy with which the organism clings
to its species-characteristics is the point on which it is mortal. One
is, [tr. note: sic] in fact, as much justified in speaking of a struggle
to retain these characteristics as to speak of a struggle for existence."

Man has been able greatly to modify many vegetable productions. Witness
the comparatively recent changes in the potato plant. The small, almost
worthless tubers of the wild potato have changed, under the force of
intelligent cultivation, to the large, starchy, nutritious vegetables,
which furnish so many people a large portion of their food. Mind has
been at work; mind and nature have changed the size, the quality, the
productiveness of the _solatium tubcrosum;_ but neither mind nor nature,
nor both combined, have, so far as we know, ever in the slightest degree
changed the species. Potatoes are potatoes still, and always will be.
The present law of vegetation is that intelligent cultivation of almost
any plant will either change the original in one way or another, or,
what is more likely, will produce several distinct varieties; but that
all these changed forms are but mere modifications of the original
species, and that, when deprived of intelligent cultivation, they all
tend to revert to the original form. It is true that we see many and
very diverse varieties of certain species, especially those that have
received the most attention from the hands of man. The dog, for
instance, exists as the great, shaggy Newfoundland or St. Bernard, or as
the tight girted greyhound, as the petted poodle or the despised "yellow
dog;" but in every case he is a dog, and not a wolf, and his fellow dogs
recognize him as such, too. Hens differ amazingly; new breeds
periodically come into existence and into fashion;