Fig. 93. Professor James D. Dana.

With what fidelity has geology deciphered the records of this wonderful history! We marvel that so many secrets of the silent ages have been found out. And yet we run over their chronicles as if but the annals of the last year. How immense a field for the imagination to sweep over! What amazing intervals of time to contemplate! what gigantic operations to trace! And yet we behold from the beginning the action of the same physical forces as are

in action to-day. The immutable and omnipresent forces of chemistry first held the elements under sway. Affinity, gravitation, caloric, electricity, in their varying operations, have wrought out the diverse phases of the modern earth. The plan of operations has been equally uniform. Igneous forces pressing upward-oceanic waters bearing downward and outward. An incipient wrinkle, a growing ridge, an upheaved cordillera. The ocean bed was made for the primeval waters. The place for the continents was marked out in earliest time, and each successive event contributed consistently to the final consummation. Even their outlines were foreshadowed in the trend of those primal ridges which made a mockery of dry land before a living thing had appeared upon the earth. And when the finishing touch was to pass over the globe, we find it effected by the same general agency as piled up miles of strata and raised granite summits to the clouds. An upheaval, a submergence, and another upheaval constitute the last three. chapters of the history. Who can contemplate this identity of agencies, this persistence of plan and perfection of results, without being impressed that One Intelligence has planned the scheme and guided the blind forces from the beginning to the accomplishment of the long-anticipated end?

CHAPTER XXVIII.

METHOD IN THE HISTORY OF LIFE.

N

ATURE has always issued her bulletins. It is a most interesting fact in the history of the animal creation that Nature advertised her plans in the very earliest creative acts. In our study of the relics of the primeval ages we do not find the grand and fundamental purposes of Infinite Wisdom unfolding themselves by degrees as type after type of organic life made its advent upon our planet. It is quite true that the full development of Nature's schemes can only be apprehended in the ultimate results, and that, with our highest wisdom, we are continually surprised at the wealth of resources exposed in the unfolding of a simple plan. But Nature had her plans, and these were mature in the very beginning. All possible contingencies being foreseen, no amendments or modifications have been necessitated by the growth of successive populations and the march of human improvement. The outlines of Nature's grand methods were announced in her initial creative efforts. It was thus in the plan of continental development; it was thus in the plan of the animal creation. It is only in the infinite flexibility of her plans, and in the inexhaustible richness of their filling up, that Nature transcends all the possibilities of human expectation.

To the geologist no fact is more familiar or more patent than the simultaneous introduction upon the earth of three of the four fundamental plans of animal structure which in the following ages were to sport into the infinite variety

of individual forms that diversify the surface of the earth at the present day. Saying nothing about the solitary Eozoon, which stands inscrutable, isolated, and mysterious in the remote ages of Eozoic Time, like a desolate islet in the midst of a dark, and trackless, and tempest-beaten sea, we find that upon the very threshold of Paleozoic Time representatives of Radiates, Molluscs, and Articulates burst into multifarious being almost simultaneously. So nearly simultaneous was the appearance of each of these types, that all hypothesis of their genealogical succession is rationally precluded. The doctrine of development finds great discountenance in the very first of the facts from which such a doctrine ought to derive its support. Later in the history of the world Vertebrates made their advent, and thus were laid the four corner-stones on which Nature has built the superstructure of the animal creation. Among all the multitudes of organic forms which have been disentombed from the cemeteries of the solid rocks, we have found none which were not conformed to one of the four fundamental types announced in the beginning. Here is no caprice, here is no chance, but the constancy, and order, and persistence of intelligence, foresight, and fixed purpose.

When this grand procession of organic forms was marshaling for its movement through time, the Supreme Intelligence sent it forward in four columns, in each of which was dominant one of the four ideas of structure. But as Nature did not range her four columns in linear order, but set them abreast of each other, so she was equally far from bringing forward the subordinate divisions of each column or plan in any thing like a fixed progressive succession. Neither the highest and most exalted forms, nor the lowest and most humble, were ordained to take absolute precedence. In the sub-kingdom of Radiates the type was

introduced by Echinoderms, Acalephs, and Protozoans, the two highest and the lowest of the four classes. True coral animals perhaps made their appearance a little later. In the sub-kingdom of Molluscs all the classes stand abreast on their first advent; in that of Articulates, the two lower classes, Crustaceans and Worms, preceded by a long interval the Insecteans; and in the sub-kingdom of Vertebrates the classes followed each other in regular gradational succession. Thus we see that, so far as class-groups are concerned, it is impossible to reduce the order of succession to any general formula. How is it with the orders of the respective classes? Among Echinoderms, Cystideans appeared before the successively higher Crinideans, Starfishes, and Sea- urchins; among Acalephs, the horny Graptolites appeared before the Coral-builders; among Protozoans, the Sponges, which ally themselves to Polypi, appeared before the lowest types-always disregarding the mysterious Eozoön. On the whole, the order of succession among the groups, based upon relative rank, is, with Radiates, from below upward. With Molluscs we find the straight and simple Orthoceratites preceding the higher Cephalapods; the arcuate and the entire-mouthed Gasteropods leading the higher spiral and flesh-eating families; the asiphonal Lamellibranchs antedating those with more complete respiratory apparatus, and the horny-shelled Lingula and Discina, among Brachiopods, appearing before the stony-shelled and stony-armed Spirifers and Terebratulas. Among the Articulate and Vertebrate classes the gradational succession of the various orders is tolerably perfect. But I must refrain from alluding to specific facts. The following grand generalization rests on a broad survey of data upon which it would be inappropriate, in this place, to enter.

There is no successional relation between the four subkingdoms of animals, nor even between the several classes