the structure of the snake or of the whale. Darwin does attempt to explain by disuse the sightless eyes of some fishes found in caves, but on the much more signal degradation of the snake and the whale he is silent.

Huxley indirectly suggests a solution1 by extending the doctrine of the struggle for existence to the molecules in the germ-cell.

"It is a probable hypothesis," he says, "that what the world is to organisms in general, each organism is to the molecules of which it is composed. Multitudes of these, having diverse tendencies, are competing with one another for opportunity to exist and multiply, and the organism as a whole is as much the product of the molecules which are victorious as the fauna or flora of a country is the product of the victorious organic beings in it. On this hypothesis hereditary transmission is the result of the victory of particular molecules contained in the impregnated germ."

Expression of type may possibly be the result of the victory of the Specific life-force of either parent in a competition for the control of the molecules that determine expression, but that, if we are disposed to consider such 1 Darwiniana, p. 115.

speculations, is very different from a conflict between the molecules themselves; for in this case we might expect the frequent appearance of animals with diminished organs, and others with theirs enlarged.

The hypothesis is developed by Professor Weissman in his Germinal,' where he recognises that neither natural selection nor varying external conditions of existence will wholly account for degradation.

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Germ-plasm," he says, "must be altered -the whole vital particles of which it is composed"; and again, "Neither natural selection nor varying differences of life will wholly account for variation, which is completed by profound processes of selection in the germ-plasm."

This he calls "Germinal Selection."

The necessary modification is brought about by what Professor Weissman calls "determinants," "that appropriate nourishment in the germ-plasm for the particular organs they produce-each battles stoutly for its food, the stronger appropriates part of the share of the weaker neighbours, who ultimately disappear, and with them the part of the organism they represent.

Applying this doctrine to the case of the snake, the "determinants" of the organs of

locomotion in the germ-plasm of the antecessor were not sufficiently powerful to appropriate their share of nourishment in the germ-plasm, and so the organs of locomotion ultimately disappeared, and if we assume that the "determinants" of the backbone were the robbers, the increased number of the vertebræ would be accounted for. But this extraordinary hypothesis, for which Darwin is not responsible, does not explain how the fore-legs of the whale were converted into fins, nor how the hind-legs came to be replaced by a tail.

1

Huxley says: "Every hypothesis is bound to explain, or at any rate not be inconsistent with, the whole of the facts it professes to account for; and if there is a single one of these facts which can be shown to be inconsistent with (I do not merely mean inexplicable by, but contrary to) the hypothesis, the hypothesis falls to the ground-it is worth nothing."

Common-sense reviewing the facts of retrogression must, we venture to assert, come to the conclusion that the Darwinian theory not only does not satisfactorily explain, but is at variance with, the phenomena.

1 Darwiniana, p. 463.

CHAPTER VIII.

VARIATION.

FROM our observations of animals we may safely conclude that no two are absolutely identical.

The differences are of three distinct kinds :

The difference among animals of admittedly the same race. This we call "Variation in expression of type"; Deviation (also among animals of the same race) in one or more parts from the normal type. This occurs but rarely, usually in a single individual, and is not hereditary. This difference. may be called "accidental" (? spontaneous) variation; and

Persistent hereditary differences between two races-viz., specific variation.

As usual in Nature, no hard line can be drawn between these different classes, and in some cases it may be difficult to determine

the category to which a difference belongs. In the human species, for example, it is sometimes impracticable to distinguish between variety of expression and the specific variation that indicates a distinct race.

Variety of Expression.

We are all familiar with the infinite variety of expression, both in face and figure, among individuals of the same human race, and we all recognise that a particular expression may be more or less hereditary in a family. We also know that a family expression may be more or less affected by the conditions of existence of the individual. But common-sense tells us that these differences of expression do not indicate any tendency towards specific variation. Careful observers may also detect similar differences of expression in the same breed of domestic animals, and even of wild species. But, as Darwin points out, the differences among domestic animals of the same race, and especially those that arise under what is called selective breeding," are much greater than among wild species.

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When, however, the differences between the best and worst specimens of any domestic