reptiles passes to the birds last named from the Dinosauria rather than from the Pterodactyls, through Archeopteryxlike forms to the ordinary birds. Finally, he has thrown out the suggestion that the celebrated footsteps left by some extinct three-toed creatu es on the very ancient sandstone of Connecticut were m: de, not, as hitherto supposed, by true birds, but by more or less ornithic reptiles. But even supposing all that is asserted or inferred on this subject to be fully proved, it would not approach to a demonstration of specific origin by minute modification. And though it harmonizes well with "Natural Selection," it is equally consistent with the rapid and sudden development of new specific forms of life. Indeed, Prof. Huxley, with a laudable caution and moderation too little observed by some Teutonic Darwinians, guarded himself carefully from any imputation of asserting dogmatically the theory of "Natural Selection," while upholding fully the doctrine of evolution.

4

But, after all, it is by no means certain, though very probable, that the Connecticut footsteps were made by very ornithic reptiles, or extremely sauroid birds. And it must not be forgotten that a completely carinate bird (the Archeopteryx) existed at a time, when, as yet, we have no evidence of some of the Dinosauria having come into being. Moreover, if the remarkable and minute similarity of the coracoid of a pterodactyl to that of a bird be merely the result of function, and no sign of genetic affinity, it is not inconceivable that pelvic and leg resemblances of Dinosauria to birds may be functional likewise, though such an explanation is, of course, by no means necessary to support the view maintained in this book.

But the number of forms represented by many individuals, yet by no transitional ones, is so great, that only two

4 A bird with a keeled breastbone, such as almost all existing birds possess.

or three can be selected as examples. Thus those remarkable fossil reptiles, the Ichthyosauria and Plesiosauria, ex

THE ARCHEOPTERYX (OF THE OOLITE STRATA).

tended, through the secondary period, probably over the greater part of the globe. Yet no single transitional form has yet been met with in spite of the multitudinous individuals preserved. Again, with their modern representa

SKELETON OF AN ICHTHYOSAURUS.

tives, the Cetacea, one or two aberrant forms alone have been found, but no series of transitional ones indicating minutely the line of descent. This group, the whales, is a very marked one, and it is curious, on Darwinian principles,

that so few instances tending to indicate its mode of origin should have presented themselves. Here, as in the bats, we might surely expect that some relics of unquestionably incipient stages of its development would have been left.

The singular order Chelonia, including the tortoises, turtles, and terrapins (or fresh-water tortoises), is another instance of an extreme form without any, as yet known, transitional stages. Another group may be finally mentioned, viz., the frogs and toads, anourous Batrachians, of which we have at present no relic of any kind linking them on to the Eft group on the one hand, or to reptiles on the other.

The only instance in which an approach toward a series of nearly-related forms has been obtained is the existing horse, its predecessor Hipparion, and other extinct forms. But even here there is no proof whatever of modification by minute and infinitesimal steps; a fortiori no approach to a proof of modification by "Natural Selection,” acting upon indefinite fortuitous variations. On the contrary, the series is an admirable example of successive modification in one special direction along one beneficial line, and the teleologist must here be allowed to consider that one motive of this modification (among probably an indefinite number of motives inconceivable to us) was the relation

ship in which the horse was to stand to the human inhabitants of this planet. These extinct forms, as Prof. Owen remarks," "differ from each other in a greater degree than do the horse, zebra, and ass,” which are not only good zoological species as to form, but are species physiologically, i. e., they cannot produce a race of hybrids fertile inter se.

As to the mere action of surrounding conditions, the same professor remarks: "Any modification affecting the density of the soil might so far relate to the changes of limb-structure, as that a foot with a pair of small hoofs, dangling by the sides of the large one, like those behind the cloven hoof of the ox, would cause the foot of Hipparion, e. g., and a fortiori the broader based three-hoofed foot of the Palæothere, to sink less deeply into swampy soil, and be more easily withdrawn than the more concentratively simplified and specialized foot of the horse. Rhi noceroses and zebras, however, tread together the arid plains of Africa in the present day; and the horse has multiplied in that half of America where two or more kinds of tapir still exist. That the continents of the Eocene or Miocene periods were less diversified in respect of swamp and sward, pampas, or desert, than those of the Pliocene period, has no support from observation or analogy."

Not only, however, do we fail to find any traces of the incipient stages of numerous very peculiar groups of animals, but it is undeniable that there are instances which appeared at first to indicate a gradual transition, yet which instances have been shown, by further investigation and discovery, not to indicate truly any thing of the kind. Thus at one time the remains of Labyrinthodonts, which, up till then, had been discovered, seemed to justify the opinion that, as time went on, forms had successively appeared 5 "Anatomy of Vertebrates," vol. iii., p. 792. • Ibid., p. 793.

with more and more complete segmentation and ossification of the backbone, which, in the earliest forms, was (as it is in the lowest fishes now) a soft, continuous rod or

TRILOBITE.

notochord. Now, however, it is considered probable that the soft backboned Labyrinthodon Archegosaurus was an immature or larval form," while Labyrinthodonts, with completely developed vertebræ, have been found to exist among the very earliest forms yet discovered. The same may be said regarding the eyes of the trilobites, some of the oldest forms having been found as well furnished in that respect as the very last of the group which has left its remains accessible to observation.

Such instances, however, as well as the way in which marked and special forms (as the Pterodactyls, etc., before referred to) appear at once in and similarly disappear from the geological record, are of course explicable on the Darwinian theory, provided a sufficiently enormous amount of past time be allowed. The alleged extreme, and probably great, imperfection of that record may indeed be pleaded But it is an excuse. Nor is it possible to deny

in excuse.

8

As a tadpole is the larval form of a frog.

8 As Prof. Huxley, with his characteristic candor, fully admitted in his lecture on the Dinosauria before referred to.