As this physiological development of the eye offers an explanation of that organ's imperfections, grounded on the ordinary method of perpetuating human existence, so the selective development of Mr. Darwin and Mr. Spencer affords an adequate solution of the corresponding difficulty in the original construction of the human eye. "The rudimentary eye," says Mr. Spencer, "consists of a few pigment grains under the outermost dermal layer; and hence we may infer that the rudimentary vision is constituted by the wave of disturbance which a sudden change in the state of the pigment grains propagates through the body." This finest of optical instruments is shown to be "produced by metamorphoses of the skin." In the eye "all is tegumentary save that which has to appreciate the impressions which the modified integument concentrates upon it." The tissues of some inferior animals are sensitive to the light; and Mr. Spencer thinks that the light itself may aid in setting up "modifications by which the nervous parts of visual organs are formed," though the particular completeness of the organ "must have arisen by the natural selection of favourable variations."1

.

This brings us directly to the Darwinian theory of evolution, the theory of modification through natural selection: Mr. Darwin begins with the simplest organ which can be called an eye, or, even lower, with a nerveless aggregage of pigment cells, incapable of distinct vision and serving only to distinguish light

1 H. Spencer's Psychology, p. 533; Biology, p. 305, 1st edit.

from darkness. In certain starfishes there occur slight depressions in the pigment layer surrounding the nerve, and these depressions are filled with gelatinous matter projecting like the cornea in higher animals. This peculiarity, according to M. Jourdain, does not "form an image, but concentrates the luminous rays and renders their perception more easy." And in this concentration of the rays, Mr. Darwin recognises the first and most important step towards the formation of a true picture-making eye; for, placed at the right distance from the concentrating apparatus, an image will be formed at "the naked extremity of the optic nerve." In this way an optic nerve may be converted into an optical instrument

as perfect as is possessed by any member of the Articulate class." In fishes and reptiles the range of gradations of dioptric structure is said by Owen to be very great. Even in man the crystalline lens is formed in the embryo by an accumulation of cells lying in the fold of the skin, as is "the vitreous body from embryonic subcutaneous tissue." Thus by innumerable gradations we pass from the production of "a simple and imperfect eye to one complete and perfect, the eye ever varying, and the variations benefiting the animal which was the subject of them, and transmitted as a valuable bequest, under the agency of this great principle, Natural Selection, to countless generations in unbroken succession."1

The validity of this reasoning was easily recognised 1 The Origin of Species, pp. 144-146.

by men eminent in science and literature, and the Darwinian theory is now so firmly established, that even Orthodoxy sometimes smiles approval. Helmholtz, referring to the identical character of practical adaptations in all physiological organs, asserts that there is perhaps no case in which adaptation to function can be so minutely traced as that of the eye, and adds, "Here the result which may be reached by innumerable generations working under the Darwinian Law of Inheritance coincides with what the highest Wisdom may have devised beforehand." In an essay on the Aim and Progress of Physical Science, Helmholtz says of this theory: "It shows how adaptability of structure in organisms can result from a blind rule of a law of nature, without any intervention of intelligence;" and in the Academy 1 he both recognises its value as a principle which enables us to connect and account for phenomena hitherto held to be inexplicable, and affirms that the Darwinian Law of the Struggle for Existence "gives undoubtedly a possible explanation of the wonderful adaptations to purpose throughout organic nature. It indicates one method of explanation; there may be others which are unknown to us."

In his Natural History of Creation, Professor Haeckel devoted six lectures to a well-digested statement of Mr. Darwin's views, and enlarged, says Mr. Huxley, on the service which the Origin of Species has rendered "in favouring what he terms the causal or mechanical view of living nature, as opposed to the 1 Academy, October 9, 1869.

teleological or vitalistic view." Mr. Fiske quotes from Haeckel's Morphology a sentence which shows that the German philosopher discerned in Darwin's discovery the definitive overthrow of the Design argument in its application to organisms. Schleiden, again, is an involuntary witness to the same truth; and Huxley, while recording his belief in a wider teleology, based on the fundamental proposition of Evolution, echoes the verdict of Haeckel when he says: "The teleology which supposes that the eye, such as we see it in man or one of the higher vetebrata, was made with the precise structure which it exhibits for the purpose of enabling the animal which possesses it to see, has undoubtedly received its death-blow." 1

We submit, then, that the "impressive instance" selected by Mr. Mill to afford a measure of the strength or weakness of the entire argument from design fails to establish the contemplated proposition. To the hypothesis of an Omnipotent Intelligence as Creator of the world it is radically opposed; to the hypothesis of an Intelligent Constructor, immeasurably powerful, though limited in efficiency, it is at least not very favourable, both because the structure of the eye discloses imperfections discreditable to a human artificer, and because it shows that adaptation can result from "blind affinities" without any intervention of intelligence.

To the argument which assumes limitation in a Divine Creator we shall return in the sequel of this essay.

CHAPTER VIII.

SPECIAL ADAPTATION-THE BEE.

IF the most impressive case of apparent design fails to support the hypothesis of an Omnipotent Creatoror shall we say of a quasi-omnipotent Creator?-it might scarcely be deemed necessary to examine cases of an inferior degree of impressiveness. There are, however, some signal instances of alleged purpose which it is desirable to notice, as the recurrence of such startling plausibilities, if left unexplained, tends to inspire a mental uneasiness, and even awaken a suspicion of the soundness of the previous reasoning, or of the correctness of the observations on which that reasoning is grounded. Of these instances, the most surprising is the cell-making instinct of the bee. Not only does the construction of the cell seem to imply the possession of a peculiar architectural talent by the bee, but the remarkable configuration which it exhibits suggests that, besides its ostensible purpose of general accommodation, it answers the particular purpose of saving wax while storing honey or pollen. Of this particular purpose M. Réaumur had some surmise. Accordingly, he proposed to M. König, a pupil of Bernouilli, the following problem: What must be the exact form of a hexagonal structure terminating in a pyramid of three