are lineal descendants of some other and generally extinct species, in the same way as the acknowledged varieties of any one species are the descendants of that species. Furthermore, I am convinced that natural selection has been the main but not the exclusive means of modification.'

If asked how far he extends the doctrine of the mutability of species, he replies:

'The question is difficult to answer, because the more distinct the forms are which we may consider, by so much the arguments fall away in force. But some arguments of the greatest weight extend very far. All the members of whole classes can be connected together by chains of affinities, and all can be classified on the same principle, in groups subordinate to groups. Fossil remains sometimes tend to fill up very wide intervals between existing orders. Organs in a rudimentary condition plainly show that an early progenitor had the organs in a fully developed state; and this in some instances necessarily implies an enormous amount of modification in the descendants. Throughout whole classes various structures are formed on the same pattern, and at an embryonic age the species closely resemble each other. Therefore I cannot doubt that the theory of descent with modification embraces all the members of the same class. I believe that animals have

descended from at most only four or five progenitors, and plants from an equal or lesser number.

'Analogy would lead me one step further, namely, to the belief that all animals and plants have descended from one prototype. But analogy may be a deceitful guide. Nevertheless all living things have much in common, in their chemical composition, their germinal vesicles, their cellular structure, and their laws of growth and reproduction. We see this even in so trifling a circumstance as that the same poison often similarly affects plants and animals; or that the poison secreted by the gall-fly produces monstrous growths on the wild rose or oak-tree. Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form into which life was first breathed.

'As all the living forms of life are the lineal descendants of those which lived long before the Silurian epoch, we may feel certain that the ordinary succession by generation has never once been broken, and that no cataclysm has desolated the whole world. Hence we may look with some confidence to a secure future of equally inappreciable length. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress toward perfection.

'It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being growth with reproduction; inheritance which is almost implied by reproduction; variability from the indirect and direct action of the external conditions of life, and from use and disuse; a ratio of increase so high as to lead to a struggle for life, and as a consequence to natural selection, entailing divergence of character, and the extinction of less improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved1.'

1 Professor Sedgwick has communicated to the Cambridge Philosophical Society an examination of the evidence bearing on

GENERAL REFLECTIONS.

These various speculations on the subject of Fossil plants and animals, and the origin and progress of life, may perhaps, to the student of exact science, appear little more than the chase of a phantom, a wandering after unattainable truth. There is, however, something seductive in the problem of the origin of life, and one who has entered on this charmed path, will seldom leave it without reluctance. Vain and ill-judged as are some of these attempts, they ought perhaps not to be visited with the heavy condemnation which sometimes has been heaped upon them. Men may have mistaken views about the diluvial catastrophe; false conceptions regarding electricity as the agent of imparting life; wrong notions about the nature of atoms, and yet not reason, at least intentionally, as 'atheists', denying the incessant watchfulness of God over the arrangements which he has appointed. It is hard to believe this of any serious thinker, even of Lucretius, however strongly he may contend for the regular operation of natural laws, in opposition to the capricious meddling of those monstrous personifications of human passions, which were accepted for deity by the 'too superstitious' men of Athens and Rome. Erroneous opinions have but their day, and are, perhaps, less mischievous than the indolence which acquiesces in dull and incurious conformity with whatever may reign for the moment. Truth, or what appears such to human reason, operating on real facts and just inferences, this is the end of scientific research; while we seek it, let us not be too much troubled if some run in courses wide of our own, and ask questions we think not likely to be answered. If we do not ourselves believe the origin of created life to be discoverable by a creature limited to the observation of sensible phenomena, why should we restrain the enterprise of those who, vainly striving after something that is unattainable or fabulous, may yet win much that is accessible, valuable and real?

According to most of the hypotheses we have been considering, the forms, structures and habits of life, which we now circumscribe by specific characters, however distinct these may seem to be, are only constant for this moment, slowly varying through this period, as they have varied in preceding periods, possibly then at a greater rate than now. The forms that now are have had a long series of progenitors, gradually changing from the earliest times; many of the earlier races of a great common stock having