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(in one volume) and has had a wide circulation. Its fifth carefully revised edition, published in this country, contains the most exact presentation of the author's views. This book promised a successor in which the facts on which the theory rested should be more fully presented. After a considerable delay this appeared, under the title of "Animals and Plants under Domestication," in two volumes. In this, besides presenting such facts as he had proposed to bring forward, the author also broached a new and remarkable theory called "Pangenesis," designed to be supplementary of his main hypothesis, of which more hereafter. These works, but especially the earlier one, excited a wide and profound interest. One point, however, was still left in some uncertainty: whether the author would extend his theory to include the origin of man, and if he did this in regard to man as an animal, whether he would also include under the operations of the same theory his higher intellectual and moral nature. Mr. Darwin's disciples were somewhat divided about the matter. All possibility of doubt has been finally removed by the publication of his two volumes on "The Descent of Man," in which the broadest ground is frankly taken of the derivation of man's whole nature from lower and still lower animal forms, until at last all organisms are ultimately derived by the simple process of "Natural Selection," or (as it is otherwise called) "the survival of the fittest," from one common source. In the case of man, Mr. Darwin traces back the probable line of the chain as far as some creature resembling "the larvae of marine Ascidians."
It is scarcely more than one quarter of this last work that is immediately concerned with the subject of its title; the remaining volume and a half being occupied with the development of a fresh supplementary hypothesis, entitled "Sexual Selection." The former supplementary hypothesis, although considered by its author as important to the completeness of his main theory, is yet one which he is willing to have set aside by those who still adhere to "Natural Selection"; the latter he makes essential as being, in all the higher. forms of
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life, an important co-operating agency in the change of hereditary structures.
The theory of Darwin is to be distinguished from the theory of evolution, as one special hypothesis is to be distinguished from a vastly more general one in which it is included. If Darwinism were proved true, it would of course establish, so far as the forms of life on this earth are concerned, the theory of evolution; but if Darwinism were proved false, evolution would have lost nothing but the discomfiture of one and just now, perhaps, the most popular one-of the supposable theories of its modus operandi. Among the most ble and zealous opponents of Darwinism are to be reckoned some of the strongest supporters of evolution. It is impossible, therefore, to discuss the Darwinian theory without saying something on the general subject of evolution, and it should be kept in mind that, on the one hand, while arguments in favor of Darwinism all go to establish evolution, those in favor of evolution generally do but afford standing ground for, and do not enter on the proof of, Darwinism; and, on the other hand, arguments against evolution are equally conclusive against Darwinism, while those against Darwinism specifically, scarcely affect the more general subject of evolution.
Mr. Darwin's main theory may be thus stated: every plant as well as animal transmits to its offspring a general likeness to itself; along with the general likeness thus inherited, each individual has also slight differences which may be of any kind and tending in any direction (the causes of these variations being scarcely at all understood, Mr. Darwin frequently speaks of them as "accidental," although fully believing them to be under the control of laws not yet discovered); all plants and animals tending to increase in number in geometrical progression, while the total vegetable and animal population of the world (apart from man and his agency) remains nearly stationary, there arises among them all a severe struggle for existence; in this struggle those individuals will survive and transmit offspring which are best adapted to the conditions of life in which they are placed, that is, "the fittest will sur
vive"; if now there come about any change in the conditions of life, either from a change in the earth itself, or from the spread of any species into a different part of the earth, the slight variations among the offspring of any plant or animal will determine which individuals will be most likely to survive, and so again among their offspring, until these "slight individual differences" have been gradually accumulated into races, species, genera, etc., etc.; at the same time a portion of the offspring continuing ordinarily under unchanged conditions, will continue itself unchanged, and thus, for the most part, the old species will in some localities be continued along with the new under other conditions; theoretically, such a process should present every possible gradation of plant and animal from the lowest to the highest, but practically so small a part of their remains is preserved, and of that part science has as yet examined only such a minute fraction, that the absence of the connecting links is sufficiently explained; the time during which organic life has existed upon our globe is practically infinite.
Mr. Darwin by no means denies that other causes, such, e.g. as outward circumstances of heat and cold, etc., may have had a direct effect in the modification of species; but these he considers as altogether secondary, the main law by which all diversities of plants and animals have been produced being natural selection, or the survival of the fittest.
It will be observed that the theory rests upon a number of data, some of which will be universally admitted, while others are more or less seriously questioned by scientific men. It may be well in advance to call attention to two points as those in which the theory stands most in need of evidence first, the extent to which the accumulation of differences is possible, and secondly, the length of time required for the purpose; while the absence of remains of intermediate forms will doubtless be considered as a further point which requires a fuller explanation. To these points we shall recur.
The reception accorded to this and to Mr. Darwin's other hypotheses has been various. Among those exclusively devo
ted to natural science, "Natural Selection" has awakened universal attention. Perhaps by the larger, certainly by the more demonstrative, portion of them it has been fully accepted, and in Germany more fully than anywhere else, and it has called forth an already considerable literature in its defence and support. By others, and those among men entitled to speak confidently upon such a subject, it is more or less completely rejected. By Mr. Wallace, who was himself an independent originator of the same theory, and by others, its general truth is fully admitted, but its applicability to man is denied. Some distinguished men of science, as
Huxley, accept it ardently, but with the reserve that certain facts such as the infertility of hybrids — which now militate against the theory shall hereafter receive an explanation. It is probably accepted by all naturalists as explaining more satisfactorily than had previously been done the variation within narrow limits of species under changed conditions of life; but this can hardly be called an acceptance of the theory, since it does not at all reach to the dimensions of the subject with which Mr. Darwin has undertaken to grapple. Among men devoted to other branches of science there has been less occasion for an expression of opinion; but, on mathematical and astronomical grounds, Sir W. Thompson has undertaken to show that the demands it makes upon time are quite inadmissible.
With the general public it has had what may be called "an immense run." Theories of evolution or of transmutation of species in various forms have always obtained a transient popularity on their first enunciation, as undertaking to bring some of the most obscure problems of the world. under the operation of familiar causes, and as definitely extending the region of LAW over what it was supposed must in some unknown way lie within its boundaries. None of these theories have rested upon so large a portion of known truth, none have been worked out in connection with such an immense observation of facts, and none have found an advocate whose candor so won upon our confidence; while
his command of style fixed our attention, and his own untiring earnestness enlisted our sympathy. When to this is added the open adhesion to, and strenuous advocacy of, the theory by several men already well-known in their successful attempts to popularize the teachings of other branches of science, it is not to be wondered at that Darwinism should have almost at once occupied the public ear, without regard to the evidence on which it rests or the real cogency of the arguments by which it is sustained. So far as the reception of a theory by those competent to pronounce upon it is to be regarded as a test of its truth, it is evident that this test has in this case only very lately begun to be applied. The sifting of the evidence, argument upon the proper inferences to be drawn from it, the questioning of the force of its analogies, the weighing of objections, are processes which are not to be accomplished in a moment, nor to be satisfactorily concluded by the application of a very few minds. What is to be the ultimate issue yet remains to be seen, and it is by no means inconceivable that another ten years may see the Darwinian theories considered as insufficient to include within their generalizations the broader domain of observation. This has already repeatedly occurred with the more or less similar theories that have preceded them, as those of Lamarck and of the author of the Vestiges of Creation.
There is one feature of the discussion, as hitherto conducted, which cannot be left quite unnoticed the absence of any reference to the scriptures by the disputants on either side. We must rejoice that doctrinal statements and the language of sacred devotion are not bandied about in such a discussion, as they might once have been. But the scriptures. have also a purely historical value, and that in regard to a period of which there is no other authentic record, and which is of importance in the present controversy. The monuments of Egypt are appealed to; but of the scriptural representations of man's primeval state, of the bearing of its histories upon the extent and the diffusion of the population of the world, and a multitude of kindred topics, we hear almost nothing.