THE BASSALIAN REALM.

At indefinite distances below the surface, even in the tropics, we find strange forms of animal life which differ, not only specifically and generically from those of the superincumbent water, as well as from those of the cold extremes of the globe, but sometimes represent even peculiar families. Those forms which live at moderate depths, existing as they do, in cold water, are related to, or even belong to, the polar faunas, but as we go still deeper we find still other assemblages of animals. Those of the lowest horizons are often wonderfully modified, and the deep-sea explorations of recent years have brought to light many remarkable forms. Among fishes, for example, are certain types that have long been known from stragglers from the lesser deep, such as the Saccopharyngidæ, Nemichthyidæ, Notacanthidae, Chauliodontidæ, Stomiatidæ, Paralepidide, Alepisaurididæ, Alepocephalidae, Regalecida, Trachypteridæ, Berycidae,* Brotulidæ, Macruridæ, and Ceratiidæ, several of which have been greatly increased of late. Other types have been discovered comparatively recently, as the Eurypharyngidæ, Bathylagide, Bathythrissidæ, Halosauridae, and Chiasmodontidæ. It is obvious, then, that we have, in such an aggregate, a combination of forms very different from any of the superficial faunas we have heretofore considered. We will be justified, therefore, in recognizing for them another realm, which we may call Bassaliaf or the Bassalian realm. But caution is timely that it is rather a heterogeneous one, and may hereafter require restriction. The data now available are insufficient, however, for differentiating what are, doubtless, the several constituents or regions of this realm.

One of the characteristic features of the Bassalian animals appears to be their wide dispersion and range. The same species may recur at opposite points of the globe, and they appear to be restricted less by latitude and longitude than by bathymetrical influ

*The Holocentridæ represent another type.

+ Bacau, Doric Greek equivalent of Bus, the deep, and áía, an assemblage.

ences. Most of the species hitherto found, it is true, have been obtained only about one locality, but it must be remembered that comparatively few individuals have been found, and their acquisition is often due to happy accidents rather than special collecting. On general principles, we are prepared to expect such a wide range. In the abyssal depths, which these animals inhabit, the conditions are perfectly uniform, and have so remained practically for geological ages, and it is, therefore, quite natural that among such forms we should find representatives of types that long ago disappeared from other parts of the globe.

It will be observed that I have given for the several realms names with a uniform termination, employing the suffix gæa for the inland and alia for the marine ones; the former has been frequently used before; the latter is a transliteration of the Ionic Greek ánia, (an assembly or gathering,) and is selected on account of the flavor or reminiscence it involves of the salt of the sea, or the sea itself. I think myself that such a system of nomenclature will be convenient on accout of dissociating our ideas of geographical realms from precise geographical regions, and also emphasizing the contrast between the inland and marine faunas. Whether they shall be adopted or not, however, must be left for individual prefer

ence.

Permit me now to indicate certain desiderata, and how our knowledge of zoogeography may be extended. Full catalogues of all the animals found at specific points will be especially useful, but to insure their usefulness, data should be given respecting their seasonal or permanent sojourn, their abundance, the depths at which they live, and the temperature of the water at various seasons. Great caution should be exercised, too, in admitting forms which may be simply adventitious wanderers, for the cacathes acquisitionis may impose serious obstacles to the proper appreciation of zoogeographical principles. Of course, I do not mean that the

*

Compare ʊvákiɑ (from đó, and áλw) to assemble or, radically, come together around the salt.

asual visitants to a country should be ignored, but I do think that t is a wrong to science to enumerate, for examples, an European vagrant to America, never found but once, and not likely to recur again for an indefinite time, if ever, or an American bird that has been once found in Britain, in a line with the well-known members of the respective faunas. Their place would be most natural in an appendix or foot note, and they should at least be without the serial numeration, if such is given, of the catalogue of permanent and seasonal members of the fauna. Let me also protest, as I have done several times before, against the incorporation of Bassalian types with the species of littoral faunas nearest to them geographically. With catalogues and data, such as I have indicated, at hand, we could soon determine, as closely as practicable, the limits of most of our faunas, and the general attention now paid to natural history holds out the hope that the coming time may not long be deferred. In conclusion, I submit a few deductions that naturally result from our observations.

A distinction is to be made between the territory occupied by an association of animals and the occupants thereof, and the limits of faunas cannot be exactly correlated with territory, except in rare

cases.

The significance of animal types as indicators of zoogeographical regions is, other things being equal, in ratio to their recent development.

The fresh-water types are the best indicators of the early relations of the respective regions.

The flying, and especially migratory, types are the most accordant with the actual relations of land areas.

Temperature is a prime factor, and land a secondary, in the distribution of marine animals.

The lay of the land is a primary, and temperature a secondary, factor in the distribution of inland animals.

CERTAIN PHASES IN THE GEOLOGICAL HISTORY OF THE NORTH AMERICAN CONTINENT, BIOLOGICALLY CONSIDERED.*

By CHARLES A. WHITE.

It is quite certain that there has never been a time in the history of mankind when the thoughts of men were so eagerly turned to biological subjects as they are to-day; nor has there ever before been a time when an intelligent knowledge of them was so broadly diffused among cultivated persons. An earnest desire is everywhere manifested by such persons to obtain substantial knowledge concerning the animal and vegetable life of the earth, and of the broad significance of that life, which is revealed by a comparative study of its myriad forms. The investigator immediately finds that this subject, although it is so comprehensive and so complex, is only a fragment of a great history of life, which extends back through unnumbered ages. He finds himself at once confronted by questions concerning successive multitudes of former denizens of the earth, the physical conditions which prevailed when they existed, the probable lines of descent by which they came into being, and by which their successors have come down to the present time; and the manner in which those lines have probably originated and been preserved from destruction through successive geological periods.

This prevalent spirit of inquiry among men has been the cause of a vast amount of patient and exhaustive research, and it has also resulted in a large accumulation of knowledge. But it cannot be denied that every investigating naturalist, although he may fully accept the doctrine of evolution, finds the subject of the origin and derivation of the various groups of animals that now inhabit the earth, and those which have inhabited it during past geological time, to be beset with many difficulties and uncertainties.

* Presidential Address delivered at the Fourth Anniversary Meeting of the Society, January 25, 1884, in the Lecture Room of the U. S. National Museum.