CHAPTER XI.
SPECIFIC GENESIS.
Review of the statements and arguments of preceding chapters .-- Cumulative argument against predominant action of "Natural Selection."-- Whether anything positive as well as negative can be enunciated .-- Constancy of laws of nature does not necessarily imply constancy of specific evolution .-- Possible exceptional stability of existing epoch .-- Probability that an internal cause of change exists .-- Innate powers must be conceived as existing somewhere or other .-- Symbolism of molecular action under vibrating impulses .-- Professor Owen's statement .-- Statement of the Author's view .-- It avoids the difficulties which oppose "Natural Selection."-- It harmonizes apparently conflicting conceptions .-- Summary and conclusion.
Having now severally reviewed the principal biological facts which bear upon specific manifestation, it remains to sum up the results, and to endeavour to ascertain what, if anything, can be said _positively_, as well as negatively, on this deeply interesting question.
In the preceding chapters it has been contended, in the first place, that no mere survival of the fittest accidental and minute variations can account for the incipient stages of useful structures, such as, _e.g._, the heads of flat-fishes, the baleen of whales, vertebrate limbs, the laryngeal structures of the newborn kangaroo, the pedicellariae of Echinoderms, or for many of the facts of mimicry, and especially those last touches of mimetic perfection, where an insect not only mimics a leaf, but one worm-eaten and attacked by fungi.

[Page 221] Also, that structures like the hood of the cobra and the rattle of the rattlesnake seem to require another explanation.
Again, it has been contended that instances of colour, as in some apes; of beauty, as in some shell-fish; and of utility, as in many orchids, are examples of conditions which are quite beyond the power of Natural Selection to originate and develop.
Next, the peculiar mode of origin of the eye (by the simultaneous and concurrent modification of distinct parts), with the wonderful refinement of the human ear and voice, have been insisted on; as also, that the importance of all these facts is intensified through the necessity (admitted by Mr.Darwin) that many individuals should be similarly and simultaneously modified in order that slightly favourable variations may hold their own in the struggle for life, against the overwhelming force and influence of mere number.
Again, we have considered, in the third chapter, the great improbability that from minute variations in all directions alone and unaided, save by the survival of the fittest, closely similar structures should independently arise; though, on a non-Darwinian evolutionary hypothesis, their development might be expected _a priori_.

We have seen, however, that there are many instances of wonderfully close similarity which are not due to genetic affinity; the most notable instance, perhaps, being that brought forward by Mr.Murphy, namely, the appearance of the same eye-structure in the vertebrate and molluscous sub-kingdoms.

A curious resemblance, though less in degree, has also been seen to exist between the auditory organs of fishes and of Cephalopods.

Remarkable similarities between certain placental and implacental mammals, between the bird's-head processes of Polyzoa and the pedicellariae of Echinoderms, between Ichthyosauria and Cetacea, with very many other similar coincidences, have also been pointed out.
Evidence has also been brought forward to show that similarity is sometimes directly induced by very obscure conditions, at present quite {222} inexplicable, _e.g._ by causes immediately connected with geographical distribution; as in the loss of the tail in certain forms of Lepidoptera and in simultaneous modifications of colour in others, and in the direct modification of young English oysters, when transported to the shore of the Mediterranean.
Again, it has been asserted that certain groups of organic forms seem to have an innate tendency to remarkable developments of some particular kind, as beauty and singularity of plumage in the group of birds of paradise.
It has also been contended that there is something to be said in favour of sudden, as opposed to exceedingly minute and gradual, modifications, even if the latter are not fortuitous.