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But let that pass. In another place the author makes it clear that the explanations of to-day, including his own, do not exhaust the subject, for he says "it is incumbent on us to discover the cause of the orderly origin of every character. The nature of such a law we cannot even dream of at present, for the causes of the majority of vertebrate adaptations remain wholly unknown."
And, on the other hand, every individual organism, from the Amœba up to the most complex vertebrate, is, in its structure, its form, its functions, a stupendous marvel of adaptation to its end and of co-ordination of the parts to the whole, and of the whole and its parts to the functions of the organism, the functions of nutrition, self-maintenance, reproduction, maintenance of the species, and so on.
He also devoted much of his attention to the exploration of the Rocky Mountain region, and found that there, in the strata of the ancient lake beds, records of the age of mammals had been made and preserved with a fulness surpassing that of any other known region on earth. The profusion of vertebrate remains brought to light was almost unbelievable. Prof.
When we think of the enormous number of variations, all in the same direction, that we must suppose to be accumulated before the passage from the pigment-spot of the Infusorian to the eye of the mollusc and of the vertebrate is possible, we do not see how heredity, as we observe it, could ever have determined this piling-up of differences, even supposing that individual efforts could have produced each of them singly.
While of the divergent divisions and subdivisions of the human race many have undergone changes not constituting an advance; while in some the type may have degraded; in others it has become decidedly more heterogeneous. The civilized European departs more widely from the vertebrate archetype than does the savage.
March had out the vertebrate, and was consulting one of its glittering ribs and glancing up from it at a house before which they stood. "Yes, it's the number; but do they call this being ready October first?"
The shells were chiefly periwinkles; there were also mussels, the large claws of crabs, the bones of vertebrate fishes and land animals, as well as some hard slabs of pottery resembling the baking-pans used by the wilder tribes at the present day. Among them, the labourers were startled by coming upon human bones, in irregular positions and at unequal depths, huddled and jumbled together.
We saw that at one time the evolutionist was puzzled by the clean division of animals into Invertebrate and Vertebrate, and the sudden appearance of the backbone in the chronicle: he was just as much puzzled by the sharp division of our plants into Cryptogams and Phanerogams, and the sudden appearance of the latter on the earth during the Coal-forest period.
Are we, then, to suppose that some extremely ancient mammal continued androgynous, after it had acquired the chief distinctions of its class, and therefore after it had diverged from the lower classes of the vertebrate kingdom? This seems very improbable, for we have to look to fishes, the lowest of all the classes, to find any still existent androgynous forms.
Subsequent investigations have brought to light a variety of facts of the same order, the most curious and striking of which are those which prove the existence, in the mesozoic epoch, of a series of forms intermediate between birds and reptiles two classes of vertebrate animals which at present appear to be more widely separated than any others.
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