30 
ANNALS NEW YORK ACADEMY OF SCIENCES 
ment for derivation during descent. Rudimentary organs were considered 
with much interest and readily explained by Darwin as vestiges of structures 
which were useful to the plant in earlier stages of its existence. The facts 
of geographic distribution were eagerly examined as bearing on the theory 
of descent, and Darwin’s writings abound in speculations relative to their 
significance. He was inclined to combat the geologic theory of former 
land connections of present existing continents, as not satisfactorily account¬ 
ing for many features of geographic distribution, though he ultimately 
agreed with this theory to some extent. He closely studied the natural 
means by which seeds are transported over great distances and also inquired 
into the vitality of seeds. 
The title of the “Origin” was a subject of considerable doubt in his 
mind, and in 1857, two years before it was printed, he had proposed to call 
it “Natural Selection.” The title “Origin of Species by Means of Natural 
Selection” is, if taken literally, somewhat misleading and has occasioned 
considerable discussion. The subtitle — “Or the Preservation of Favored 
Races in the Struggle for Life” — is a more accurate statement of his theory. 
On November 23, 1856, he wrote to Dr. Hooker: 
The formation of a strong variety, or species, I look at as almost wholly due to 
the selection of what may be incorrectly called chance variations. Again, the 
slight differences selected, by which a race or species is at last formed, stand, as I 
think can be shown in the far more important relation to its associates than to external 
conditions. 
Darwin’s great contribution to the subject of evolution was the incon¬ 
trovertible proof adduced by him that living species are modified descendants 
of preexisting species, 'and that the modifications are brought about by 
natural causes. His observations led him to the conclusion that the modi¬ 
fications were all minute, gradual and cumulative. We know that they may 
also be considerable and abrupt and that they are cumulative because favora¬ 
ble changes are preserved. 
How, then, do the modifications or primordial variations, either large 
or small, arise ? Is variation an innate essential quality, or is it induced 
by external environmental factors ? Proof of environmental agencies 
having at least something to do with it in plants seems to be accumulating, 
as the experimental work carried on by MacDougal and by Gager at the 
New York Botanical Garden appears to imply. 
I think that we may now safely outline the methods of formation of 
species somewhat as follows: Through causes which are not yet at all well 
known, but by means of which agencies external to the germ-cells certainly 
may have a part, the offspring of a plant grown from seed differ more or 
