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On the other hand, a distinguished American scientist, Dr. W. C. Wells, in 1813 succeeded in arriving at the principle of natural selection ; but he failed to draw any conclusions from it, except in regard to human beings. From this, and from the fact that his theory was not supported by any considerable number of observations, it was productive of even less influence on the thought of the scientific world than Lamarck's theory had been.
In Charles Darwin's hands, however, the doctrine did not fail to be applied, not merely to
“It is certain that these weapons are not provided for their defence against other adversaries, because the females in these species are without this armor. The final cause of this contest amongst the males seems to be, that the strongest and most active animal should propagate the species, which should thence become improved.”
Also (as has been suggested to me by Professor G. M. Harmon of Tufts College), Dr. Darwin seems to have appreciated the fact of a struggle for existence, and to have recognized the result of the process of survival of the fittest, even though he did not quite understand how it was brought about. He says,
“On the other hand, swiftness of wing has been acquired hy hawks and swallows to pursue their prey; and a proboscis of admirable structure has been acquired by the bee, the moth, and the humming-bird, for the purpose of plundering the nectaries of flowers. All which seem to liave been formed by the original living filament, excited into action by the necessities of the creatures which possess them, and on which their existence depends."
The Italics are my own.
all animals, but to all plants as well. And, wherever facts to verify the theory in any particular were lacking, Darwin set himself to work to obtain them, from books, by conversation with breeders of animals and with gardeners, or by long series of patient experiments. No one can read the “ Origin of Species,” or that vast storehouse of information, “ Animals and Plants under Domestication,” without being greatly impressed by the way in which Darwin made the observations of all men tributary to his own great work. No back number of a horticultural magazine or a poultry-breeder's journal seems to have escaped his attention, while (among more strictly scientific sources of information) he studies the Malay Archipelago through Wallace's eyes, and New Zealand and Australia through those of Dr. Hooker. The great Amazon basin becomes familiar to him through the descriptions of Bates and others, while Central America is known through the studies of Mr. Belt; and so on with a long list of other regions.
From the keepers of the English and foreign zoological and botanic gardens a great fund of information was obtained. Nor should it be forgotten that Mr. Darwin's personal acquaintance with the life of some of the most interesting regions of the globe (gathered during his voyage round the world from 1831 to 1836) was extensive and profound.
To this immense fund of knowledge must be added that which he gained by his own careful experiments. His residence, Down House, and the surrounding grounds, during the whole period of his occupancy, constituted an extensive set of apparatus for botanical and zoological experiments.
Greenhouses, beehives, dovecotes, poultryyards, fields, and pastures, all were devoted to the one great work of accumulating facts about animals and plants. A single example from among the many that might be cited will show the patient persistency with which Mr. Darwin carried out any line of study: one field was left untouched for thirty years, during which time he was carrying on an elaborate investigation into the habits of the earth-worm.
It is not strange that such ability as Darwin's, so consecrated to the pursuit of science, should have been so fertile in results as to lead Wallace to say of him,
“ However much our knowledge of nature may advance in the future, it will certainly be by following in the pathways he has made clear for us; and for long years to come the name of Darwin will stand for the typical example of what the student of nature ought to be.”
And yet the development theory to-day is not, strictly speaking, “ Darwinism,” as it is so often called. Very many prominent evolutionists now feel it to be certain that various natural causes bring about much more rapid advances or changes in species than seem to have been recognized by Mr. Darwin. For many such sudden advances as that of the brine-shrimps so often mentioned, and for other phenomena not explained by natural selection, explanations have been offered by Cope, Hyatt, and Packard, among American writers on the subject, and by Henslow, Mivart, and others in Great Britain.
Mivart even goes so far as almost to repudiate the theory of natural selection, substituting for it an evolution theory of his own. With a very large number of naturalists, however, natural selection holds the first place among the causes which have given rise to species. The doctrine of descent, in some form, has gained over to its support a vast majority of the English-speaking naturalists of the world. In France it has made little progress, a fact which may be due to the powerful influence there of Cuvier and Agassiz, two most uncompromising opponents, each in his day, of all theories of organic evolution. In Germany, on the other hand, the theory has met with a most enthusiastic reception. A few naturalists, it is true, have remained unconvinced; but such authorities as Adolph Schmidt, Fritz Müller, and, above all, Haeckel, have carried out Darwin's line of argument with great success. To Haeckel, indeed, the name of “the German Darwin” has often, though incorrectly, been applied.
In his fondness for controversy, as well as in the enthusiastic and speculative manner in which the great German zoologist has applied the principles of evolution to the construction of one vast genealogical tree for the animal, and of another for the vegetable kingdom, he is as little like Darwin as one well could be. But by his profound and far-reaching knowledge of the animal kingdom, his brilliant, fearless style of expression, and his unsurpassed power of popularizing scientific results, Haeckel has done a great work in the cause of his favorite theory. Then, too, by his exhaustive researches concerning the structure and life-history of the sponges, he has done more than any other man utterly to break down the old idea of species. He has indeeed (as already shownl) demonstrated, that among chalk-sponges, at any rate, there are no species.
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