The identity of meaning above insisted on was, on the face of it, almost as obscure as that between "_eveque_ and bishop." Yet we know that "_eveque_" is "episc" and "bishop" "piscop," and that "episcopus" is the Latin for bishop; the words, therefore, are really one and the same, in spite of the difference in their appearance. I think I can show, moreover, that Mr. Darwin himself holds natural selection and the conditions of existence to be one and the same thing. For he writes, "in one sense," and it is hard to see any sense but one in what follows, "the conditions of life may be said not only to cause variability" (so that here Mr. Darwin appears to support Lamarck's main thesis) "either directly or indirectly, but likewise to include natural selection; for the conditions determine whether this or that variety shall survive."[357] But later on we find that "the expression of conditions of existence, so often insisted upon by the illustrious Cuvier" (and surely also by the illustrious Lamarck, though he calls them "_circonstances_") "is fully embraced by the principle of natural selection."[358] So we see that the conditions of life "_include_" natural selection, and yet the conditions of existence "_are fully embraced by_" natural selection, which, I take it, is an enigmatic way of saying that they are one and the same thing, for it is not until two bodies absolutely coincide and occupy the same space that the one can be said both to include and to be embraced by the other. The difficulty, again, of understanding Mr. Darwin's meaning is enhanced by his repeatedly writing of "natural selection," or the fact that the fittest survive in the struggle for existence, as though it were the same thing as "evolution" or the descent, through the accumulation of small modifications in many successive generations, of one species from another and different one. In the concluding and recapitulatory chapter of the 'Origin of Species,' he writes:-- "Turning to geographical distribution, the difficulties encountered _on the theory of descent with modification_ are serious enough;"[359] and in the next paragraph, "As, according to _the theory of natural selection, &c._," the context showing that in each case descent with modification is intended. Again:-- "On the theory of the _natural selection_ of successive, slight, but profitable, modifications,"[360] that is to say, on the theory of the survival of the fittest; while on the next page we find "_the theory of descent with modification_," and "_the principle of natural selection_," used as though they were convertible terms. Again:-- "The existence of closely allied or representative species in any two areas implies, _on the theory of descent with modification, &c._;"[361] and, in the next paragraph, "_the theory of natural selection_, with its contingencies of extinction and divergence of character," is substituted as though the two expressions were identical.