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Now, even if we take the most favorable view of the theory of the transmissibility of acquired characters, and assume that the ostensible acquired character is not, in most cases, the more or less tardy development of an innate character, facts show us that hereditary transmission is the exception and not the rule. How, then, shall we expect it to develop an organ such as the eye?
We are not going to enter here into the controversies over the transmissibility of acquired characters; still less do we wish to take too definite a side on this question, which is not within our province. But we cannot remain completely indifferent to it.
Let us say, then, how the problem seems to us to present itself, and in what direction an attempt might be made to solve it. After having been affirmed as a dogma, the transmissibility of acquired characters has been no less dogmatically denied, for reasons drawn a priori from the supposed nature of germinal cells.
Moreover, while the Darwinian theory of natural selection, supplemented as it was by the adoption of the Lamarkian factors, the effect of use and disuse and the assumed transmissibility of acquired character, merely attempted to explain the mode in which the changes in organic life have taken place upon the earth, the evolutionary hypothesis put forth by Mr.
There is, indeed, one point on which both those who affirm and those who deny the transmissibility of acquired characters are agreed, namely, that certain influences, such as that of alcohol, can affect at the same time both the living being and the germ-plasm it contains.
Still more slow may be the moulding of the still more refractory germ-plasm, if such there be. But the moulding process goes on parallel in the two cases. But Weismann's argument rests not merely upon any difficulty or impossibility of the transmissibility of acquired characteristics.
But if, perchance, experiment should show that acquired characters are transmissible, it would prove thereby that the germ-plasm is not so independent of the somatic envelope as has been contended, and the transmissibility of acquired characters would become ipso facto conceivable; which amounts to saying that conceivability and inconceivability have nothing to do with the case, and that experience alone must settle the matter.
In Nägeli's theory initial tendency is overwhelmingly dominant; in Weismann's, natural selection is almighty. Weismann's followers have received the name of Neo-Darwinians. The so-called Neo-Lamarckian school believes in the transmissibility of acquired characteristics, and of at least particular effects of use and disuse. The one theory is neither more nor less Darwinian than the other.
Since his death, moreover, his disciples have tended to split into two schools. On the one hand, Weismann has rejected the Lamarckian factors, the effect of use and disuse upon organs, and the transmissibility of acquired characters. The importance of these factors has been emphatically re-asserted, on the other hand, by Lankester and others.
LAFARGUE, La théorie darwinienne. I am well aware that in these last years, perhaps in consequence of the relations between Darwinism and socialism, consideration has again been given to the objections to the theory of Darwin, made by Voegeli, and more recently by Weismann, on the hereditary transmissibility of acquired characters. See SPENCER, The Inadequacy of Natural Selection, Paris, 1894.
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