Again, we have the very curious horned flies,[[73]] which agree indeed in a common peculiarity, but in one singularly different in detail, in different species and not known to have any protecting effect.
Amongst plants, also, we meet with the same peculiarity. The great group of Orchids presents a number of species
which offer strange and bizarre approximations to different animal forms, and which have often the appearance of cases of mimicry, as it were in an incipient stage.
The number of similar instances which could be brought forward from amongst animals and plants is very great, but the
examples given are, it is hoped, amply sufficient to point towards the conclusion which other facts will, it is thought, establish, viz. that there are causes operating (in the evocation of these harmonious diverging resemblances) other than "Natural Selection," or heredity, and other even than merely geographical, climatal, or any simply external conditions.
Many cases have been adduced of striking likenesses between different animals, not due to inheritance; but this should be the less surprising, in that the very same individual presents us with likenesses between different parts of its body (e.g., between the several joints of the backbone), which are certainly not so explicable. This, however, leads to a rather large subject, which will be spoken of in the eighth chapter of the present work. Here it will be enough to affirm (leaving the proof of the assertion till later) that parts are often homologous which have no direct genetic relationship,—a fact which harmonizes well with the other facts here given, but which "Natural Selection," pure and simple, seems unable to explain.
But surely the independent appearance of similar organic forms is what we might expect, a priori, from the independent appearance of similar inorganic ones. As Mr. G. H. Lewes well observes,[[74]] "We do not suppose the carbonates and phosphates found in various parts of the globe—we do not suppose that the families of alkaloids and salts have any nearer kinship than that which consists in the similarity of their elements, and the conditions of their combination. Hence, in organisms, as in salts, morphological identity may be due to a community of causal connexion, rather than community of descent.
"Mr. Darwin justly holds it to be incredible that individuals identically the same should have been produced through Natural Selection from parents specifically distinct, but he will not deny that identical forms may issue from parents genetically distinct,