If, however, it is not unlikely that there is an innate tendency to deviate at certain times, and under certain conditions, it is no more unlikely that that innate tendency should be an harmonious one, calculated to simultaneously adjust the various parts of the organism to their new relations.

The objection as to the sudden abortion of rudimentary organs may be similarly met.
Professor Huxley seems now disposed to accept the, at least {104} occasional, intervention of sudden and considerable variations.

In his review of Professor Koelliker's[97] criticisms, he himself says,[98] "We greatly suspect that she" (_i.e._ Nature) "does make considerable jumps in the way of variation now and then, and that these saltations give rise to some of the gaps which appear to exist in the series of known forms." [Illustration: MUCH ENLARGED HORIZONTAL SECTION OF THE TOOTH OF A LABYRINTHODON.] In addition to the instances brought forward in the second chapter against the minute action of Natural Selection, may be mentioned such {105} structures as the wonderfully folded teeth of the labyrinthodonts.

The marvellously complex structure of these organs is not merely unaccountable as due to Natural "Selection," but its production by insignificant increments of complexity is hardly less difficult to comprehend.
Similarly the aborted index of the Potto (_Perodicticus_) is a structure not likely to have been induced by minute changes; while, as to "Natural Selection," the reduction of the fore-finger to a mere rudiment is inexplicable indeed! "How this mutilation can have aided in the struggle for life, we must confess, baffles our conjectures on the subject; for that any very appreciable gain to the individual can have resulted from the slightly lessened degree of required nourishment thence resulting (_i.e._ from the suppression), seems to us to be an almost absurd proposition."[99] [Illustration: HAND OF THE POTTO (PERODICTICUS), FROM LIFE.] Again, to anticipate somewhat, the great group of whales (Cetacea) was fully developed at the deposition of the Eocene strata.

On the other hand, we may pretty safely conclude that these animals were absent as late as the latest secondary rocks, so that their development could not have been so very slow, unless geological time is (although we shall presently see there are grounds to believe it is not) practically infinite.