Again we read:  “Domestic instincts are sometimes spoken of as actions which have become inherited solely from long-continued and compulsory habit, but this, I think, is not true.”—­Ibid., p. 214.

Again:  “I am surprised that no one has advanced this demonstrative case of neuter insects, against the well-known doctrine of inherited habit, as advanced by Lamarck.”—­[Origin of Species, ed. 1872, p. 233.]

I am not aware that Lamarck advanced the doctrine that instinct is inherited habit, but he may have done so in some work that I have not seen.

It is true, as I have more than once pointed out, that in the later editions of the Origin of Species it is no longer “the most serious” error to refer instincts generally to inherited habit, but it still remains “a serious error,” and this slight relaxation of severity does not warrant Professor Weismann in ascribing to Mr. Darwin an opinion which he emphatically condemned.  His tone, however, is so off-hand, that those who have little acquaintance with the literature of evolution would hardly guess that he is not much better informed on this subject than themselves.

Returning to the inheritance of acquired characters, Professor Weismann says that this has never been proved either by means of direct observation or by experiment.  “It must be admitted,” he writes, “that there are in existence numerous descriptions of cases which tend to prove that such mutilations as the loss of fingers, the scars of wounds, etc., are inherited by the offspring, but in these descriptions the previous history is invariably obscure, and hence the evidence loses all scientific value.”

The experiments of M. Brown-Sequard throw so much light upon the question at issue that I will quote at some length from the summary given by Mr. Darwin in his Variation of Animals and Plants under Domestication. {279} Mr. Darwin writes:—­

“With respect to the inheritance of structures mutilated by injuries or altered by disease, it was until lately difficult to come to any definite conclusion.” [Then follow several cases in which mutilations practised for many generations are not found to be transmitted.] “Notwithstanding,” continues Mr. Darwin, “the above several negative cases, we now possess conclusive evidence that the effects of operations are sometimes inherited.  Dr. Brown-Sequard gives the following summary of his observations on guinea-pigs, and this summary is so important that I will quote the whole:—­

“’1st.  Appearance of epilepsy in animals born of parents having been rendered epileptic by an injury to the spinal cord.

“’2nd.  Appearance of epilepsy also in animals born of parents having been rendered epileptic by the section of the sciatic nerve.

“’3rd.  A change in the shape of the ear in animals born of parents in which such a change was the effect of a division of the cervical sympathetic nerve.