If the primordial cell had been only capable of reproducing itself once, there would have followed a single line of descendants, the chain of which might at any moment have been broken by casualty. Doubtless the millionth repetition would have differed very materially from the original—as widely, perhaps, as we differ from the primordial cell; but it would only have differed by addition, and could no more in any generation resume its latest development without having passed through the initial stage of being what its first forefather was, and doing what its first forefather did, and without going through all or a sufficient number of the steps whereby it had reached its latest differentiation, than water can rise above its own level. The very idea, then, of reproduction involves, unless I am mistaken, that, no matter how much the creature reproducing itself may gain in power and versatility, it must still always begin _with itself again_ in each generation. The primordial cell being capable of reproducing itself not only once, but many times over, each of the creatures which it produces must be similarly gifted; hence the geometrical ratio of increase and the existing divergence of type. In each generation it will pass rapidly and unconsciously through all the earlier stages of which there has been infinite experience, and for which the conditions are reproduced with sufficient similarity to cause no failure of memory or hesitation; but in each generation, when it comes to the part in which the course is not so clear, it will become conscious; still, however, where the course is plain, as in breathing, digesting, &c., retaining unconsciousness. Thus organs which present all the appearance of being designed—as, for example, the tip for its beak prepared by the embryo chicken—would be prepared in the end, as it were, by rote, and without sense of design, though none the less owing their origin to design.