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 ments in production, and to increased skill and intelligence." It is the chief cause of that struggle for existence through which the fittest are enabled to survive, and through which the level of the race is raised.

Whether the arrivalsurvival [sic] of the fittest is due chiefly to spontaneous favorable variations, or to the partial inheritance of characters or capacities repeatedly acquired by successive generations, is a question on which Spencer took no dogmatic stand; he accepted Darwin's theory gladly, but felt that there were facts which it could not explain, and which compelled a modified acceptance of Lamarckian views. He defended Lamarck with fine vigor in his controversy with Weismann, and pointed out certain defects in the Darwinian theory. In those days Spencer stood almost alone on the side of Lamarck; it is of some interest to note that today the neo-Lamarckians include descendants of Darwin, while the greatest contemporary English biologist gives it as the view of present-day students of genetics that Darwin's particular theory (not, of course the general theory) of evolution must be abandoned.

The two volumes on The Principles of Psychology (1873) are the weakest links in Spencer's chain. There had been an earlier volume on the subject (1855), a youthfully vigorous defense of materialism and determinism; but age and thought revised this into a milder form, and padded it out with hundreds of pages of painstaking but unilluminating analysis. Here, even more than elsewhere, Spencer is rich in theories and poor in proofs. He has a theory of the origin of nerves out of intercellular connective tissue; and a theory of the genesis of instinct by the compounding of reflexes and the transmission of acquired characters; and a theory of the origin of mental categories out of the experience of the race; and