“A black feather or two, even if coupled with some lengthening of the tail, would in no way assist the cuckoo in placing its egg in the drongo’s nest. Suppose an ass were to borrow the caudal appendage of the king of the forest, pin it on behind him, and then advance among his fellows with loud brays, would any donkey of average intelligence be misled by the feeble attempt at disguise? I think not. Much less would a king-crow be deceived by a few black feathers in the plumage of a cuckoo. I do not believe that natural selection has any direct connection with the nigritude of the drongo-cuckoo.” Darwin was fully alive to this difficulty when he wrote: “As some writers have felt much difficulty in understanding how the first step in the process of mimicry could have been effected through natural selection, it may be well to remark that the process probably commenced long ago between forms not widely dissimilar in colour” (_Descent of Man_, 10th Ed., p. 324). Such a statement is of course quite inconsistent with the Neo-Darwinian position. “The conclusion which emerges most clearly,” writes Poulton (_Essays on Evolution_, p. 232), “is the entire independence of zoological affinity exhibited by these resemblances; and one of the rare cases in which Darwin’s insight into a biological problem did not lead him right was when he suggested that a former closer relationship may help us to a general understanding of the origin of mimicry. The preservation of an original likeness due to affinity undoubtedly explains certain cases of mimicry, but we cannot appeal to this principle in the most remarkable instances.” It is unnecessary to labour this point. It is surely evident to everyone with average intelligence that, until the resemblance between two forms has advanced a considerable way, the likeness cannot be of utility to either, or at any rate of sufficient utility to give its possessor a survival advantage in the struggle for existence. Until it reaches this stage, natural selection cannot operate on it. It is therefore absurd to look upon natural selection as the direct cause of the origin of the likeness. When once a certain degree of resemblance has risen, it is quite likely that in some cases natural selection has strengthened the likeness. The second great objection to the Neo-Darwinian explanation of the phenomenon known as mimicry is that in many cases the resemblance is unnecessarily exact. Even as we saw how the Kallimas, or dead-leaf butterflies, carried their resemblance to dead leaves to such an extent as to make it appear probable that factors other than natural selection have had a share in its production, so do we see in certain cases of mimetic resemblance an unnecessarily faithful likeness. The Brain-fever Bird