shallows. Thus depth in the sea corresponded, in its effect upon distribution, to height on the hind.
The same idea is applied to the explanation of a similar anomaly in the Fauna of the Ægean:
"In the deepest of the regions of depth of the Ægean, the representation of a northern Fauna is maintained, partly by identical and partly by representative forms.... The presence of the latter is essentially due to the law (of representation of parallels of latitude by zones of depth), while that of the former species depended on their transmission from their parent seas during a former epoch and subsequent isolation. That epoch was doubtless the newer Pliocene or Glacial Era, when the Mya truncata and other northern forms now extinct in the Mediterranean, and found fossil in the Sicilian tertiaries, ranged into that sea. The changes which there destroyed the shallow-water glacial forms, did not affect those living in the depths, and which still survive."[1]
The conception that the inhabitants of local depressions of the sea-bottom might be a remnant of the ancient population of the area, which had held their own in these deep fastnesses against an invading Fauna, as Britons and Gaels have held out in Wales and in Scotland against encroaching Teutons, thus broached by Forbes, received a wider application than Forbes had dreamed of when the sounding machine first brought up specimens of the mud of the deep sea. As I have pointed out elsewhere,[2] it at once became obvious that the calcareous, sticky mud of the Atlantic was made up, in the main, of shells of Globigerina and other Foraminifera, identical with those of which the true chalk is composed, and the identity extended even to the presence of those singular bodies, the coccoliths and, the true nature of which is not yet made out. Here, then, were organisms, as old as the Cretaceous epoch, still alive, and doing their work of rock-making at the bottom of existing seas. What if Globigerina and the coccoliths should not be the only survivors of a world passed away, which are hidden beneath three miles of salt-water? The letter which Dr. Wyville Thomson wrote to Dr. Carpenter in May, 1868, out of which all these expeditions have grown, shows that this query had become a practical problem in Dr. Thomson's mind at that time; and the desirableness of solving the problem is put in the foreground of his reasons for urging the government to undertake the work of exploration:
"Two years ago, M. Sars, Swedish Government Inspector of Fisheries, had an opportunity, in his official capacity, of dredging off the Loffoden Islands at a depth of 300 fathoms. I visited Norway shortly after his return, and had an opportunity of studying with his father, Prof. Sars, some of his results. Animal forms were abundant; many of them were new to science; and among them was one of surpassing interest, the small crinoid, of which you have a specimen, and which we at once recognized as a degraded type of the
