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Updated: May 19, 2025
Romanes, writing in Nature, March 18, 1890, and opposing certain details of Professor Weismann's theory, so far supports it as to say that "there is the gravest possible doubt lying against the supposition that any really inherited decrease is due to the inherited effects of disuse." The "gravest possible doubt" should mean that Mr.
These characters have a remarkable way of becoming "segregated" once more that is, of appearing intact later on. While it follows from Weismann's theory that an adaptation acquired by an individual during his lifetime cannot be transmitted to his offspring, it remained for De Vries to show authoritatively that evolution can, and does, take place without this.
On the whole Osborne's verdict would seem just: The Neo-Lamarckian theory fails to explain heredity, Weismann's theory does not explain evolution. But, if the effects of use and disuse are transmitted, correlation of variation is to be expected. Muscle, nerve, and ganglion all vary in correlation because they are all used together and in like degree.
I could find no able discussion upon the whole subject in Professor Weismann's book. There was a little something here and there, but not much. Mr Herbert Spencer has not in his more recent works said anything which enables me to appeal to his authority.
For clearly the fact that the separated egg-cells grow into complete individuals shows that Weismann's theory, according to which one of the cells contained only body plasm, the other only germ plasm, is quite untenable.
Cutting off the tails of several generations of mice is not voluptuous enough to tempt a scientific Nero. It was a mere piece of one-eyedness; and it was Darwin who put out Weismann's humane and sensible eye. He blinded many another eye and paralyzed many another will also.
It is to be found in the preface which he wrote to Professor Weismann's Studies in the Theory of Descent, published in 1882. "Several distinguished naturalists," says Mr.
Wallace is endorsing Professor Weismann's view, but I have found it impossible to collect anything that enables me to define his position confidently in this respect. This is natural enough, for Mr. Wallace has entitled his book Darwinism, and a work denying that use and disuse produced any effect could not conceivably be called Darwinism. Mr.
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.
Lack of space compels us to leave unnoticed most of the exceedingly valuable suggestions of Nägeli's brilliant work. It is still less possible to do any justice in a few words to Weismann's theory. Into its various modifications, as it has grown from year to year, we have no time to enter. And we must confine ourselves to his views of variation and heredity.
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