It has been suggested by several geologists, notably by Professor S u e s s, that the Atlantic Ocean is not a true ocean like the Pacific, but is a basin of secondary and of comparativly recent formation; and Professor W o e k o f f has recently shown, in a most interesting contribution, that meteorologically also the Atlantic should be considered as a n inland sea rather than as a true ocean.
The question therefore naturally arises, is the Atlantic Ocean biologically an inland sea?
Before we can answep this question we must define an inland sea in terms of biology.
An inland sea, biologically speaking, is a more or less enclosed body of water which, connected with a n ocean, has received all of its fauna from that ocean.
Its fauna, therefore, is composed of the same types that occur in the ocean with which it is most intimately connected, with the less plastic and adaptable weeded out an-d the remainder modified in proportion to the difference between the physics and chemistry of the inland sea and that of the parent ocean.
All inland seas necessarily 'differ physically to a greater or lesser degree from the omans 'with which they are connected. Their abyssal water cannot form a part of the general abyssal circulation of the oceans, moving slowly anticlockwise about the oceanic basins, and therefore tends to become more or less stagnant and, under certain conditions, very cold. Their surface water, no longer a part of the general superficial oceanic circulation, unless there be an outlet