Herbert Spencer

by J. Arthur Thomson

But the hypothesis only serves the purpose because the constitutional units are gradually invested with the powers of effective response, co-ordination, and the like which remain the secret of the organism as a whole—the secret of life, which many think will never be read until we recognise that it is also the secret of mind.

The Germ-Cells.—According to Spencer, "sperm-cells and germ-cells are essentially nothing more than vehicles in which are contained small groups of the physiological units in a fit state for obeying their proclivity towards the structural arrangement of the species they belong to," and "if the likeness of offspring to parents is thus determined, it becomes manifest, a priori, that besides the transmission of generic and specific peculiarities, there will be a transmission of those individual peculiarities which, arising without assignable causes, are classed as spontaneous." Not only are the main characters transmitted, the same may be true of even minute details—varietal characters, like the taillessness of Manx cats, and individual congenital peculiarities such as a sixth finger; normal qualities such as swiftness in race-horses, abnormal qualities such as nervousness in man. Here Spencer was of course at one with all biologists.

Transmission of Acquired Characters.—He went on, however, to try to substantiate the proposition, which has been the subject of so much discussion, that modifications or acquired bodily characters are also transmissible, and we must follow his argument carefully.

He first points out that when a structure is altered by a change of function the modification is often unobtrusive, and its transmission consequently difficult to detect. "Moreover, such specialities of structure as are due to specialities of function, are usually entangled with specialities which are, or may be, due to selection, natural or artificial. In most cases it is impossible to say that a structural peculiarity which seems to have arisen in offspring from a functional peculiarity in a parent, is wholly independent of some congenital peculiarity of structure in the parent, whence this functional peculiarity arose. We are restricted to cases with which natural or artificial selection can have had nothing to do, and such cases are difficult to find. Some, however, may be noted."

When a plant is transferred from one soil to another it undergoes "a change of habit"; its leaves may become hairy, its stem woody, its branches drooping. "These are modifications of structure consequent on modifications of function that have been produced by modifications in the actions of external forces. And as these modifications reappear in succeeding generations, we have, in them, examples of functionally-established variations that are hereditarily transmitted." But this is a non sequitur, since the modifications may reappear merely because they are re-impressed directly on each successive generation.

Spencer notes that in the domestic duck the bones of the wing weigh less and the bones of the leg more in proportion to the whole skeleton than do the same bones in the wild duck; that in cows and goats which are habitually milked the udders are large; that moles and many cave-animals have rudimentary eyes, and so on. But all these results may be readily interpreted as due to selection of germinal variations.

The best examples of inherited modifications occur, he says, in mankind. "Thus in the United States the descendants of the immigrant Irish lose their Celtic aspect, and become Americanised.... To say that 'spontaneous variation' increased by natural selection can have produced this effect is going too far." But if the vague statement as to the Americanisation of the Irishman be correct, and if it be true that intermarriage is rare, it remains probable that the Americanisation is a modificational veneer impressed afresh on each successive generation.

"That large hands are inherited by those whose ancestors led laborious lives, and that those descended from ancestors unused to manual labour commonly have small hands, are established opinions." But if we accept the fact, it is easy to interpret the size of the hands as a stock-character correlated with a muscularity and vigour, and established by selection. The prevalence of short-sightedness among the "notoriously studious" Germans is a singularly unfortunate instance to give in support of the inheritance of functional modifications, for there is no reason to believe that short-sightedness is primarily an acquired character. Nor is it confined to readers.

Spencer twits those who are sceptical as to the transmission of acquired modifications, for assigning the most flimsy reasons for rejecting a conclusion they are averse to; but when Spencer cites the inheritance of musical talent and a liability to consumption as evidence of the transmission of functional modifications, we are reminded of the pot calling the kettle black.