The entire question of the possibility of the inheritance of acquired characters is itself at present far from being on a satisfactory basis, as we shall try to show; and Darwin’s attempt at an explanation, in his chapter on pangenesis, does not put the matter in a much more satisfactory condition.
Let us now turn our attention to a school that has grown up in modern times, the members of which call themselves Neo-Lamarckians. Let us see if they have supplied the essential evidence that is required to establish the Lamarckian view, namely, that characters acquired by the individual are transmitted to the offspring.
Lamarck’s views were adopted by Herbert Spencer, and play an important rôle in his “Principles of Biology” (1866-1871), and even a more conspicuous part in his later writings. In the former he cites, amongst other cases, that of “a puppy taken from its mother at six weeks old who, although never taught ‘to beg’ (an accomplishment his mother had been taught), spontaneously took to begging for everything he wanted when about seven or eight months old.” If tricks like this are inheritable is it not surprising that more puppies do not stand on their hind-legs?
The larger hands of the laboring classes in England are supposed to be inherited by their children, and the smaller hands of the leisure classes are supposed to be the result of the disuse of the hands by their ancestors; but even if these statements in regard to size are true, there are many other conceivable causes that may have led to this result.
Short-sightedness appears more often, it is said, in those classes of society that make most use of their eyes in reading and in writing; but if we ask for experimental evidence to show that this is due to inheritance, and not due to the children spoiling their eyes at school, there is none forthcoming. The problem is by no means so simple as the uninitiated may be led to believe.
Spencer thinks that “some of the best illustrations of functional heredity are furnished by mental characteristics.” He cites the musical faculty as one that could not have been acquired by natural selection, and must have arisen through the inheritance of acquired modifications. The explanation offered is “that the habitual association of certain cadences of speech with certain emotions has clearly established in the race an organized and inherited connection between such cadences and such emotions, ... and that by the continued hearing and practice of melody there has been gained and transmitted an increasing musical sensibility.” But a statement that the results have been acquired in this way does not supply the proof which the theory is in need of; neither does it follow that, because the results cannot be explained by the theory of natural selection, therefore, they must be explained by the Lamarckian theory.