[33] Since the above was written Prof. Lloyd Morgan has published a closely similar notice of the passage in question. “This language,” he says, “seems to savour of teleology (that pitfall of the evolutionist). The cart is put before the horse. The recognition-marks were, I believe, not produced to prevent intercrossing, but intercrossing has been prevented because of preferential mating between individuals possessing special recognition-marks. To miss this point is to miss an important segregation-factor."—(Animal Life and Intelligence, p. 103.) Again, on pp. 184-9, he furnishes an excellent discussion on the whole subject of the fallacy alluded to in the text, and gives illustrative quotations from other prominent Darwinians. I should like to add that Darwin himself has nowhere fallen into this, or any of the other fallacies, which are mentioned in the text.
[34] Of course adaptive modifications produced in the individual lifetime, and not inherited, do not concern the question at all. In this and the following paragraphs, therefore, “adaptations,” “adaptive modifications,” &c., refer exclusively to such as are hereditary, i. e. phyletic.
[35] The question as to whether natural selection has been the only principle concerned in the origination of species, is quite distinct from that as to the accuracy of the above definition.
[36] It is often objected to Darwin’s terminology, that it embraces such words as “contrivance,” “purpose,” &c., which are strictly applicable only to the processes or the products of thought. But when it is understood that they are used in a neutral or metaphorical sense, I cannot see that any harm arises from their use.
[37] Note B.
[38] Were it not that some of Darwin’s critics have overlooked the very point wherein the great value of protective colouring as evidence of natural selection consists, it would be needless to observe that it does so in the minuteness of the protective resemblance which in so many cases is presented. Of course where the resemblance is only very general, the phenomena might be ascribed to mere coincidence, of which the instincts of the animal have taken advantage. But in the measure that the resemblance becomes minutely detailed, the supposition of mere coincidence is excluded, and the agency of some specially adaptive cause demonstrated. Again, it is almost needless to say, no real difficulty is presented (as has been alleged) by the cases above quoted of seasonal imitations, on the ground that natural selection could not act alternately on the same individual. Natural selection is not supposed to act alternately on the same individual. It is supposed to act always in the same manner, and if, as in the case of a regularly recurring change in the colours of the environment, correspondingly recurrent changes are required to appear in the colours of the animals, natural selection sets its premium upon those individuals the constitutions of which best lend themselves to seasonal changes of the needful kind—probably under the influence of stimuli supplied by the changes of external conditions (temperature, moisture, &c.).
[39] For a full account of this instinct and its probable purpose, see Animal Intelligence, pp. 93-6.
[40] Both drawings are reproduced from Mr. Poulton’s paper upon the subject (Proc. Zool. Soc., June 16, 1891).
[41] Anatomy of Vertebrates, vol. iii. p. 794.
[42] The degree in which variability is indefinite, or, on the contrary, determinate, is a question which is not yet ripe for decision—nor even, in my opinion, for discussion. But I may here state the following general principles with regard to it.