That he did not take a narrow view of the process of Selection, which has so many forms and operates at so many levels, will be admitted; and we may illustrate this by showing that he had a prevision of what Roux called "intra-individual selection" or "intra-selection."
In his essay on "The Social Organism" (1860), he wrote:—
"The different parts of a social organism, like the different parts of an individual organism, compete for nutriment; and severally obtain more or less of it according as they are discharging more or less duty." (See also Essays, i. 290.) And, again, in 1876, in his Principles of Sociology, he amplified his statement thus: "All other organs, therefore, jointly and individually, compete for blood with each organ,... local tissue formation (which under normal conditions measures the waste of tissue in discharging function) is itself a cause of increased supply of materials... the resulting competition, not between units simply, but between organs, causes in a society, as in a living body, high nutrition and growth of parts called into the greatest activity by the requirements of the rest." And once more: "For clearly, if the survival of the fittest among organisms is a process of equilibration between actions in the environment and actions in the organism; so must the local modifications of their parts, external and internal, be regarded as survivals of structures, the reactions of which are in equilibrium with the actions they are subject to." Clearly Spencer had a prevision of what Roux calls "Der Kampf der Theile im Organismus" (The struggle of parts within the organism), and we have here another example of his biological insight. That Spencer was not far from the idea of a struggle between hereditary units, we see from the following passage: "In the fertilised germ we have two groups of physiological units, slightly different in their structures. These slightly different units severally multiply at the expense of the nutriment supplied to the unfolding germ—each kind moulding this nutriment into units of its own type. Throughout the process of development the two kinds of units, mainly agreeing in their proclivities and in the form which they tend to build themselves into, but having minor differences, work in unison to produce an organism of the species from which they were derived, but work in antagonism to produce copies of their respective parent-organisms. And hence ultimately results an organism in which traits of the one are mixed with traits of the other; and in which, according to the predominance of one or other group of units, one or other sex with all its concomitants is produced" (Principles of Biology, vol. i., revised ed., p. 315).
While Spencer had this wide appreciation of the scope of selection, he firmly held that biologists burdened it unjustifiably by disbelieving in the transmission of acquired characters, and, as we have seen, he gave a number of examples of phenomena which he believed the Darwinian theory minus the Lamarckian factor was quite inadequate to interpret. He went the length of saying: "Either there has been inheritance of acquired characters or there has been no evolution." Spencer indicated three general difficulties or limitations besetting the theory of Natural Selection.
(1) "The general argument proceeds upon the analogy between natural selection and artificial selection. Yet all know that the first cannot do what the last does. Natural Selection can do nothing more than preserve those of which the aggregate characters are most favourable to life. It cannot pick out those possessed of one particular favourable character, unless this is of extreme importance."
[It is admitted that we cannot prove that Natural Selection effected this or that result in the distant past, but we know that a process of discriminate elimination is a fact of life, and we argue from the present to the past. Given variations enough and time enough, it is difficult to put limits to the efficacy of selection. If in a race of birds fairly well adapted to the conditions of their life, variations occur in the length of wing, there is no theoretical difficulty in supposing that if a longer wing is advantageous, this particular favourable character may in the course of time become through selection the property of the whole race.]
(2) "In many cases a structure is of no service until it has reached a certain development; and it remains to account for that increase of it by natural selection which must be supposed to take place before it reaches the stage of usefulness."
[One variation is often correlated with another, and the stronger variation may afford point d'appui for the action of natural selection, and thus act as a cover for the incipient variation until that reaches the stage of usefulness and becomes itself of selection-value. What Spencer himself says in regard to the selection of aggregates rather than items, seems half the answer to his difficulty.
It has also been suggested that adaptive modifications may act as fostering nurses of germinal variations in the same direction. Let us suppose a country in which a change of climate made it year by year of the utmost importance that the inhabitants should become swarthy. Some individuals with a strong innate tendency in this direction would doubtless exist, and on them and their similarly endowed progeny, the success of the race would primarily, and might wholly depend. At the same time, there might be many individuals in whom the constitutional tendency in the direction of swarthiness was too weak and incipient to be of use. If these, or some of them, made up for their lack of natural swarthiness by a great susceptibility to acquired swarthiness, to becoming tanned by the sun, it is conceivable that this modification, though never taking organic root, might serve as a life-saving screen until coincident congenital variations in the direction of swarthiness had time to grow strong and become of selection value. We can also imagine that a stock without great mental ability might succeed, in conditions where a premium was put on brains, by their application and docility, till eventually innate variations in the direction of real cleverness became established in the stock. Similarly, many animals by increased 'will-power' or intelligence may survive until bodily variations of an adaptive kind arise to economise the higher energies. Here and everywhere we venture to say that the more anthropomorphic we can reasonably make our conception of organic evolution the truer it is likely to be.
A third answer to Spencer's second difficulty is afforded by Weismann's subtle theory of Germinal Selection.]