Among the wt Aeasiggcelsoar of the last two regions, oe since the 
differences between them are more of degrees than of kind, need not be 
considered Gaia ce the Eieelites of the sea water. Ohedits sts have 
determined that the water of the deep sea varies in the proportions of 
mineral nals, carbonie acid and air contained in it very much as does the 
surface water. The’ warm water of the tropics at the surface contain more 
salts and less nitrogen. As the water flows northward to the Arctic regions, 
the salts sink to the sep as ie water is cooled. Therefore, the Polar 
waters are less saline and contain more nitrogen than do the warm waters 
of the tropies. The uci of air in the water is closely related to the 
temperature, and the amount of oxygen aiatiniad gradually from the sur- 
face until about 400 fathoms are reached, when it ceases to change. 
Carbonic acid is said by some chemists not to exist in a free state i 
sea water. This, however, may well be questioned since the shells obtained 
from the deep sea are ali eroded and the devices of the animal for protection 
against erosion so apparent. Krosive agencies, like those due to carbonic 
acid found in the species inhabiting the Litoral Region, are very recognizable 
in various species found in the abyss. This fuct leads us to conclude that 
the composition of the water of the deep sea does not differ materially from 
that of any other sea water. 
The physical conditions, however, are vastly different. It is difficult to 
imagine what the pressure must be at a depth of 2,000 fathoms. Without 
doubt the pressure some points on the oceanic floor may amount to sev- 
eral tons to the square inch. Rope made impervious by tarring has been 
_ reduced one-third in its diameter by a descent into these depths. We must 
_ conclude from these facts that all the animals living in ate auptlis one 
_ subject to these conditions must have their t 
_ the free permeation ti ag water through every part of their bodies to ‘equal- 
uch a condition is possible without putting an end 
i In fishes this 
¥ condition is most noticeable, cohen some of the most flabby specimens 
are armed with very formidable teeth. We can conceive, however, that 
under the great pressure of the depths of the sea, this loose and flabby tissue 
_ may be reduced to a cordition resembling iron or steel, and the animals 
may be as lithe and active as their s hallow wer relatives. The influence. 
_ of darkness in the Abyssal Region of the se often spoken of. It isa 
curious fact that the inhabitants of the deep sea are neater destitute of visual 
_ Organs, or have excessively developed eyes, far beyond the normal of the 
_ group to which they belong. This fact is evidence that the depths are very 
_ much darker than the shallows. This is not evidence enough, however, as 
some physicists have maintained that the — are shrouded 4 in betrgeigt 27 
