Page:Popular Science Monthly Volume 77.djvu/442

436 than 200 fathoms, and that the bottom forms of the deep-sea do not rise more than 60 fathoms above the floor of the ocean, and that there is practically no life between 200 fathoms below the surface and 60 fathoms above the bottom. His later studies have, however, shown that these conclusions must be modified, for in the tropical Pacific surface forms are sometimes taken at a depth of about 300 fathoms beneath the surface, and although the surface animals do not commonly sink to depths greater than this, there is apparently a most interesting intermediate fauna of medusæ, etc., which are sometimes found at depths greater than 400 fathoms and which rarely or never rise to the surface. Agassiz clearly saw the complexities and difficulties of this problem, and realized that its solution can be reached only after many have labored upon it. Indeed, he himself was forced through lack of time to abandon its study to others.

A very rich collection of deep-sea forms then new to science was made by this expedition of the Albatross and have been described in numerous papers in the "Bulletins" and "Memoirs" of the museum at Harvard.

The most important general result was Alexander Agassiz's discovery that the deep-sea animals of the Gulf of Panama were more closely allied to those of the depths of the Caribbean Sea than the Caribbean forms were to those of the deep waters of the Atlantic. This leads him to conclude that the Gulf of Panama was once more intimately connected with the Caribbean than the latter is with the Atlantic, and thus the Caribbean Sea was at one time merely a bay of the Pacific, and has become shut off since Cretaceous times by the uplifting of the Isthmus of Panama.

In 1892 Alexander Agassiz published his general report upon this important exploration of the Panamic region, and he concludes that the Galapagos Islands have never been connected with the mainland of America, but that the ancestors of their peculiar animals and plants were drifted over the ocean by the prevailing winds and stranded upon the shores of these remote islands. He also observed that the animals of the deep sea are preponderatingly reddish or violet in color, and that blue-colored forms, such as are observed on the surface, are rare in the depths. This inclines him to suspect that the lingering remnant of sunlight which penetrates into the depths is red, but in view of the absence of observation he is cautious in advancing this suggestion.

Another paper of 1892 is his description of an interesting crinoid from the depths of the sea near the Galapagos Islands. This is a highly generalized form, and it is beautifully painted from life by Westergren, who accompanied him as artist upon the Albatross. In 1898 and 1904 he describes the deep-sea echini found off Panama, this