age onward there were on the two sides of the ocean many species of invertebrate animals, which were either identical, or so closely allied as to be possibly varietal forms. In like manner the early plants of the Upper Silurian, Devonian, and Carboniferous present many identical species; but this identity becomes less marked in the vegetation of the more modern times.

In so far as plants are concerned, it is to be observed that the early forests were largely composed of cryptogamous plants, and the spores of these in modern times have proved capable of transmission for great distances. In considering this, we can not fail to conclude that the union of simple cryptogamous fructification with arboreal stems of high complexity, so well illustrated by Dr. Williamson, had a direct relation to the necessity for rapid and wide distribution of these ancient trees. It seems also certain that some spores, as, for example, those of the Rhizocarps, a type of vegetation abundant in the Paleozoic, and certain kinds of seeds, as those named Etheotesta and Pachytheca, were fitted for flotation. Further, the periods of Arctic warmth permitted the passage round the northern belt of many temperate species of plants, just as now happens with the Arctic flora; and when these were dispersed by colder periods they marched southward along both sides of the sea on the mountain-chains. The same remark applies to northern forms of marine invertebrates, which are much more widely distributed in longitude than those farther south. The late Mr. Gwyn Jeffreys, in one of his latest communications to this Association, stated that fifty-four per cent of the shallow-water mollusks of New England and Canada are also European, and of the deep-sea forms thirty out of thirty-five; these last, of course, enjoying greater facilities for migration than those which have to travel slowly along the shallows of the coasts in order to cross the ocean and settle themselves on both sides. Many of these animals, like the common muscle and sand-clam, are old settlers which came over in the Pleistocene period, or even earlier. Others, like the common periwinkle, seem to have been slowly extending themselves in modern times, perhaps even by the agency of man. The older immigrants may possibly have taken advantage of lines of coast now submerged, or of warm periods, when they could creep around by the Arctic shores.

Mr. Herbert Carpenter and other naturalists employed on the Challenger collections have made similar statements respecting other marine invertebrates, as, for instance, the Echinoderms, of which the deep-sea crinoids present many common species, and my own collections prove that many of the shallow-water forms are common. Dall and Whiteaves have shown that some mollusks and Echinoderms are common even to the Atlantic and Pacific coasts of North America; a remarkable fact, testifying at once to the fixity of these species, and to the manner in which they have been able to take advantage of geographical changes. Some of the species of whelks common to the

Gulf of St. Lawrence and the Pacific are animals which have no special locomotive powers even when young, but they are northern forms not proceeding far south, so that they may have passed through the Arctic

seas.

In this connection it is well to remark that many species of animals. have powers of locomotion in youth, which they lose when adult, and that others may have special means of transit. I once found at Gaspé a specimen of the Pacific species of Coronula, or whale-barnacle, the C. regina of Darwin, attached to a whale taken in the Gulf of St. Lawrence, and which had probably succeeded in making that passage round the north of America which so many navigators have essayed in vain. It is to be remarked here that while many plants and marine invertebrates are common to the two sides of the Atlantic, it is different with land-animals, and especially vertebrates.

I do not know that any fossil insects or land-snails or millipedes of Europe and America are specifically identical, and of the numerous species of batrachians of the Carboniferous and reptiles of the Mesozoic all seem to be distinct on the two sides. The same appears to be the case with the Tertiary mammals, until in the later stages of that great period we find such genera as the horse, the camel, and the elephant appearing on the two sides of the Atlantic; but even then the species seem different, except in the case of a few northern forms. Some of the longer-lived mollusks of the Atlantic furnish suggestions which remarkably illustrate the biological aspect of these questions. Our familiar friend the oyster is one of these. The first-known oysters appear in the Carboniferous in Belgium and in the United States of America. In the Carboniferous and Permian they are few and small, and they do not culminate till the Cretaceous, in which there are no less than ninetyone so-called species in America alone; but some of the largest known species are found in the Eocene. The oyster, though an inhabitant of shallow water, and very limitedly locomotive when young, has survived all the changes since the Carboniferous age, and has spread itself over the whole northern hemisphere. I have collected fossil oysters in the Cretaceous clays of the coulées of Western Canada, in the Lias shales of England, in the Eocene and Cretaceous beds of the Alps, of Egypt, of the Red Sea coast, of Judea, and the heights of Lebanon. Everywhere and in all formations they present forms which are so variable and yet so similar that one might suppose all the socalled species to be mere varieties. Did the oyster origiate separately on the two sides of the Atlantic, or did it cross over so promptly that its appearance seems to be identical on the two sides? Are all the oysters of a common ancestry, or did the causes, whatever they were, which introduced the oyster in the Carboniferous, act over again in later periods? Who can tell?

This is one of the cases where causation and development-the two scientific factors which constitute the bases of what is vaguely called

THE

POPULAR SCIENCE

MONTHLY.

JANUARY, 1887.

WHAT MAKES THE RICH RICHER AND THE
POOR POORER.

K

BY PROFESSOR WILLIAM G. SUMNER.

ARL MARX says, "An accumulation of wealth at one pole of society indicates an accumulation of misery and overwork at the other."* In this assertion, Marx avoids the very common and mischievous fallacy of confusing causes, consequences, and symptoms. He suggests that what is found at one pole indicates, or is a symptom of, what may be found at the other. In the development of his criticisms on political economy and the existing organization of society, however, Marx proceeds as if there were a relation of cause and effect in the proposition just quoted, and his followers and popularizers bave assumed as an indisputable postulate that the wealth of some is a cause of the poverty of others. The question of priority or originality as between Marx, Rodbertus, and others, is at best one of vanity between them and their disciples, but it is of great interest and importance to notice that the doctrine that wealth at one pole makes misery at the other is the correct logical form of the notion that progress and poverty are correlative. This doctrine rests upon another and still more fundamental one, which is not often formulated, but which can be detected in most of the current socialistic discussions, viz., that all the capital which is here now would be here under any laws or institutions about property, as if it were due to some independent cause, and that some have got ahead of others and seized upon the most of it, so that those who came later have not been able to get any. If this notion about the source of capital is not true, then wealth at one pole can not cause poverty at the other. If it is

"Das Capital," i, 671.

+ On this question see Anton Menger, "Das Recht auf den vollen Arbeitsertrag," Stuttgart, 1886. This writer traces back for a century the fundamental socialistic notions. He aims to develop the jural as distinguished from the economic aspect of socialism.

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