Jewish types; but the tenth generation adds nothing to the evidence of the first, nor the ten-thousandth to the tenth. I believe that this fallacy, which destroys the whole value of the Cuvierian argument, has not before been pointed out; and even now, you may, perhaps, ask if the fixity of Species is not proved by the fact that like produces like? So far from this, that it is only by the aid of such a fact in organic nature that we can imagine _new_ species to have arisen: in other words, those who believe in the variability of Species, and the introduction of new forms by means of modification from the old, always invoke the law of hereditary transmission as the means of establishing accidental variations. Thus, let us suppose the Egyptian king to have had one hundred dogs, all of them staghounds, and no other form of dog to have existed at that time in that country; the dog species would be represented by the staghound. These staghounds would transmit to their offspring all their _specific characters_. But, as every one knows, however much dogs may resemble each other, they always present individual differences in size, colour, strength, intelligence, &c. Now, if any one of these differences should happen to become marked, and to increase by the intermarriage of two dogs similarly distinguished by the marked peculiarity, this peculiarity would in time become established by hereditary transmission, and would form the starting-point of a new race of dogs—say the greyhound—unless it were obliterated by intermarriage with dogs of the old type. In the former case, we should have two races of dogs among the descendants of those figured on the Egyptian tombs; but as one of these races would still preserve the original staghound type, Cuvier would refer to _it_ as a proof that species had not varied. We, on the other hand, should point to the greyhound as proof that animal forms _are_ variable, and that a new form had arisen from modification of the old.