these cases and the general principle of natural selection that Nature has pronounced the sentence of death upon highly specialized forms; that they have passed out of the royal line of descent for a special advantage; that if they vary at all it can only be within the restricted lines along which they have already gone so far; and that the birthright belongs to forms which have some general advantage, but are not hampered by special adaptations. These spread over the earth and from them branch off the numerous closely related and variable species that occupy all the environments of the earth. Thus Drosera, with its power to catch insects, is yet a plant like others, and has gone forth with its advantage to possess the earth. Vitis, with its climbing power, has scattered its species by the hundred over the earth. It is the modification that opens up to the species a large area, which makes it possible for the species to send out its kind into the whole earth to be everywhere modified by local influ

ences.

The principle that has been discussed is now one of the well understood corollaries of the principle of natural selection. I do not know who first called attention to it. It has probably occurred to many minds independently.

Darwin, so far as I know, never recognized it. The earliest clear statement of it that I have seen is by Prof. Joseph Le Conte in an article on "Instinct and Intelligence," 1 published in 1875, only a few months after the publication 'of Darwin's "Insectivorous Plants." He said, 'Instinct, therefore, is accumulated experience, or knowledge of many generations fixed permanently and petrified in brain-structure. All such petrifaction arrests development, because unadaptable to new conditions. They are found, therefore, only in classes and families widely differentiated from the main stem of evolution, from the lowest animals to man. Instincts are, indeed, the flower and fruit at the end of these widely differentiated branches, but flowering and fruiting arrest onward growth. In 1877, Marsh, in a discussion of the suilline type, stated the true principle when he said that ambitious offshoots have perished, while the generalized or rather unspecialized forms continue the line of life with true suilline stubbornness, 2

1 Popular Science Monthly, October, 1875, p. 664.

2 American Journal of Science, XIV. (III.), pp. 362–364.

D

XIV.

GENERAL DISCUSSIONS.

ARWIN'S general discussions of the various subjects that he worked out in such minute detail are models both of clearness and of exhaustiveness. The reasoning of the second volume of the "Variation of Animals and Plants under Domestication" is long sustained and characterized by the use of enormous numbers of facts. The latter is one of the chief characteristics of his reasoning. He was frequently compelled, as in the case of the "Origin of Species," by the limits within which he was obliged to condense his materials, to substitute general statements for long series of facts. The generalizations were condensations of the detailed facts, which were too bulky for his pages. This is the reason why his discussions leave the impression of an almost infinite reserve of evidence; and rightly seem to convey much more to the reader than is actually written on the page.

Among Darwin's many exhaustive discus

sions of the materials which he had collected, some of the most striking are his chapters on pigeons,1 in which he considered the variation of breeds, individual differences, and skeletal differences; the discussion in the second volume of the "Variation of Animals and Plants under Domestication"; the exhaustive analysis of his materials in reaching his general conclusions on the effects of cross- and self-fertilization; and his repeated discussions of the cement glands of Cirripedia, and of the parasitic and complemental males on the hermaphrodite "females," and the reasons for regarding them as such rather than as independent forms.2 But the general discussion that is typical both from the general interest of the subject and the compactness and symmetry of the argument is the work on the "Origin of Species." would be impossible to analyze such a farreaching argument without restating it. Doubtless criticisms could be made against the arrangement of materials and the order of discussion, and against the nature of the evidence adduced. It is not intended here to raise the

It

1 Variation of Animals and Plants under Domestication, Vol. I. pp. 137-235.

2 Monograph of Cirripedia, Vol. I. pp. 38, 180-293, Vol. II. pp. 23-30, 151.

question whether his argument as a whole is sound and carries conviction with it, but simply to repeat that, considering the materials that Darwin had to work with and the difficulties. under which he labored, the argument is finished, and will always serve as a type of probable proof.

Darwin himself has given the reasons for this state of his great discussion. He has complained that he must be a very slow thinker; and doubtless the truth in this complaint accounts for the fact that his thinking was always so thorough. He also bewailed the fact that he experienced great difficulty in writing.1 He felt that he had great ability to get things wrong end foremost in his expression, and said. that he spent a great deal of time in arranging the matter in his larger works. From one point of view it is a paradox that such a man should accomplish so much that has proved of permanent value. But the lack of natural felicity of expression and inability to think rapidly, together with his persistence, insured him against the vice of saying things nimbly, and furnished the guaranty that whatever he did would be thorough. It is safe to say that a far larger proportion of false and inaccurate 1 Life and Letters, Vol. I. p. 80.