theory brings us the other way to the same result. In his view, not only all the individuals of a species are descendants of a common parent, but of all the related species also. Affinity, relationship, all the terms which naturalists use figuratively to express an underived, unexplained resemblance among species, have a literal meaning upon Darwin's system, which they little suspected, namely, that of inheritance. Varieties are the latest offshoots of the genealogical tree in "an unlineal" order; species, those of an earlier date, but of no definite distinction; genera, more ancient species, and so on. The human races, upon this view, likewise may or may not be species according to the notions of each naturalist as to what differences are specific; but, if not species already, those races that last long enough are sure to become so. It is only a question of time.

How well the simile of a genealogical tree illustrates the main ideas of Darwin's theory the following extract from the summary of the fourth chapter shows:

"It is a truly wonderful fact-the wonder of which we are apt to overlook from familiarity—that all animals and all plants throughout all time and space should be related to each other in group subordinate to group, in the manner which we everywhere behold-namely, varieties of the same species most closely related together, species of the same genus less closely and unequally related together, forming sections and sub-genera, species of distinct genera much less closely related, and genera related in different degrees, forming sub-families, families, orders, sub-classes, and classes. The several subordinate groups in any class cannot be ranked in a single file, but seem rather to be clustered round points, and these round other points, and so on in almost endless cycles. On the view that each species has been independently created, I can see no explanation of this

great fact in the classification of all organic beings; but, to the best of my judgment, it is explained through inheritance and the complex action of natural selection, entailing extinction and divergence of character, as we have seen illustrated in the diagram.

"The affinities of all the beings of the same class bave sometimes been represented by a great tree. I believe this simile largely speaks the truth. The green and budding twigs may represent existing species; and those produced during each former year may represent the long succession of extinct species. At each period of growth all the growing twigs have tried to branch out on all sides, and overtop and kill the surrounding twigs and branches, in the same manner as species and groups of species have tried to overmaster other species in the great battle for life. The limbs divided into great branches, and these into lesser and lesser branches, were themselves once, when the tree was small, budding twigs; and this connection of the former and present buds by ramifying branches may well represent the classification of all extinct and living species in groups subordinate to groups. Of the many twigs which flourished when the tree was a mere bush, only two or three, now grown into great branches, yet survive and bear all the other branches; so with the species which lived during long-past geological periods, very few now have living and modified descendants. From the first growth of the tree, many a limb and branch has decayed and dropped off; and these lost branches of various sizes may represent those whole orders, families, and genera, which have now no living representatives, and which are known to us only from having been found in a fossil state. As we here and there see a thin, straggling branch springing from a fork low down in a tree, and which by some chance has been favored and is still alive on its summit, so we occasionally see an animal like the Ornithorhynchus or Lepidosiren, which in some small degree connects by its affinities two large branches of life, and which has apparently been saved from fatal competition by having inhabited a protected station. As buds give rise by growth to fresh buds, and these, if vigorous, branch out

and overtop on all sides many a feebler branch, so by generation I believe it has been with the great Tree of Life, which fills with its dead and broken branches the crust of the earth, and covers the surface with its ever-branching and beautiful ramifications."

It may also be noted that there is a significant correspondence between the rival theories as to the main facts employed. Apparently every capital fact in the one view is a capital fact in the other. The difference is in the interpretation. To run the parallel ready made to our hands:

"The simultaneous existence of the most diversified types under identical circumstances, the repetition of similar types under the most diversified circumstances, . the unity of plan in otherwise highly-diversified types of animals, . . . . the correspondence, now generally known as special homologies, in the details of structure otherwise entirely disconnected, down to the most minute peculiarities, . . . . the various degrees and different kinds of relationship among animals which (apparently) can have no genealogical connection, . . . . the simultaneous existence in the earliest geological periods, . . . . of representatives of all the great types of the animal kingdom, . . . . the gradation based upon complications of structure which may be traced among animals built upon the same plan; the distribution of some types over the most extensive range of surface of the globe, while others are limited to particular geographical areas, . . . . the identity of structures of these types, notwithstanding their wide geographical distribution, . . . . the community of structure in certain respects of animals otherwise entirely different, but living within the same geographical area,

....

...

. . . the connection by series of special structures observed in animals widely scattered over the surface of the globe,. . . . the definite relations in which animals stand to the surrounding world, . . . . the relations in which individuals of the same

1 Agassiz, "Essay on Classification; Contributions to Natural History," p. 132, et seq.

...

species stand to one another, . . . . the limitation of the range of changes which animals undergo during their growth, . the return to a definite norm of animals which multiply in various ways, . . . . the order of succession of the different types of animals and plants characteristic of the different geological epochs, . . . . the localization of some types of animals upon the same points of the surface of the globe during several successive geological periods, . . . . the parallelism between the order of succession of animals and plants in geological times, and the gradation among their living representatives, . . . . the parallelism between the order of succession of animals in geological times and the changes their living representatives undergo during their embryological growth,1. the combination in many extinct types of characters which in later ages appear disconnected in different types, . . . . the parallelism between the gradation among animals and the changes they undergo during their growth, . . . . the relations existing between these different series and the geographical distribution of animals, . . . the connection of all the known features of Nature into one system-”

.

In a word, the whole relations of animals, etc., to surrounding Nature and to. each other, are regarded under the one view as ultimate facts, or in their ultimate aspect, and interpreted theologically; under the other as complex facts, to be analyzed and interpreted

1 As to this, Darwin remarks that he can only hope to see the law hereafter proved true (p. 449); and p. 338: "Agassiz insists that ancient animals resemble to a certain extent the embryos of recent animals of the same classes; or that the geological succession of extinct forms is in some degree parallel to the embryological development of recent forms. I must follow Pictet and Huxley in thinking that the truth of this doctrine is very far from proved. Yet I fully expect to see it hereafter confirmed, at least in regard to subordinate groups, which have branched off from each other within comparatively recent times. For this doctrine of Agassiz accords well with the theory of natural selection."

scientifically. The one naturalist, perhaps too largely assuming the scientifically unexplained to be inexplicable, views the phenomena only in their supposed relation to the Divine mind. The other, naturally expecting many of these phenomena to be resolvable under investigation, views them in their relations to one another, and endeavors to explain them as far as he can (and perhaps farther) through natural causes.

But does the one really exclude the other? Does the investigation of physical causes stand opposed to the theological view and the study of the harmonies between mind and Nature? More than this, is it not most presumable that an intellectual conception realized in Nature would be realized through natural agencies? Mr. Agassiz answers these questions affirmatively when he declares that "the task of science is to investigate what has been done, to inquire if possible how it has been done, rather than to ask what is possible for the Deity, since we can know that only by what actually exists;" and also when he extends the argument for the intervention in Nature of a creative mind to its legitimate application in the inorganic world; which, he remarks, "considered in the same light, would not fail also to exhibit unexpected evidence of thought, in the character of the laws regulating the chemical combinations, the action of physical forces, etc., etc." Mr. Agassiz, however, pronounces that "the connection between the facts is only intellectual"-an opinion which the analogy of the inor

1

1 Op. cit., p. 131.-One or two Bridgewater Treatises, and most, modern works upon natural theology, should have rendered the evi-, dences of thought in inorganic Nature not "unexpected."