Philologists will most certainly reject the law as laid down by Agassiz. But I must also protest against the comparison admitted by this illustrious naturalist. If I attribute a _language_ to animals, I do not forget how rudimentary it is. I recollect that no animal has ever learnt the language of another. I know too well the distance there is between _animal interjections_ and _articulate speech_, and I am as well aware as anyone that to use such an instrument, so as to produce from it _true languages_, can only be accomplished by the superior intelligence of man. Agassiz, when he had arrived at this point, must have felt that he had lost himself, and that, in trying to harmonise the idea of a single human species with that of several races of distinct origin, he was entering an endless labyrinth. His last work betrays the signs of this embarrassment only too clearly. It is probably in the hope of escaping from it that the author has finally even denied the existence of species. After having again rejected the criterion drawn from crossing and degrees of fertility, he adds: “With it disappears in its turn the pretended reality of species as opposed to the mode of existence of genera, families, orders, classes and branches. Reality of existence is, in fact, possessed by individuals alone.” Thus, from adhering solely to morphology, from a disregard of the physical side of the question, from having allowed themselves to be guided by a logic which is only founded upon incomplete data, Agassiz and Darwin have arrived at a similar result. Both have disregarded this great fact, intelligible to common sense, demonstrated by science, and which governs everything in zoology, as it does in botany, the division, namely, of organised beings into elementary and fundamental groups which propagate in space and time. But Darwin, starting from the _phenomena_ of _variations_ which are presented by these beings, considers _species_ as only _races_. Agassiz, entirely preoccupied with the _phenomena_ of _fixity_, finally considers _individuals_ only as existing in living nature. Both forget that the great Buffon passed successively to both these extremes only to return again to the doctrine which includes and explains all facts, and which may be summed up in these words: distinction of _race_ and _species_.