without any intervention of descent." According to this we are to conclude that products of unlike species, that is species which vary, are descended from one another, but those of similar species not. But even this is not altogether correct, for he ventures to say of the varying species, "The part played by descent is on the contrary a very secondary activity of nature." There is heredity, then, but it is only to be reckoned as a factor of the second class. Let us be glad that heredity of which Herr Duehring has said so much that is evil and mysterious is at least let in by the back door. It is just the same with natural selection, since after all his moral indignation with respect to the struggle for existence by means of which natural selection fulfils itself he suddenly exclaims, "The most important constituent is to be found in the conditions of life and cosmic conditions, while natural selection as set forth by Darwin may be considered as secondary." Natural selection still exists, even if a factor of the second class, like the struggle for existence, and the clerical malthusian surplus-population theory. That is all, for the rest Herr Duehring refers us to Lamark.
Finally, he warns against misuse of the terms metamorphosis and evolution. Metamorphosis, he says, is a very obscure notion, and the concept of evolution is only admissible in so far as a law of evolution can be really proved. Instead of either of these expressions we should employ the term "composition" and then everything would be all right. It is the same old story over again, Herr Duehring is satisfied if we change the names. If we speak of the evolution of the chicken in the egg we give rise to confusion because we have only an incomplete knowledge of the law of evolution. But if we speak of its "composition" everything becomes clear.
