844 
ganic life was impossible in the great depths. 
It has been proved, however, that animals 
of all classes, except the higher vertebrates, 
have been dredged from even the deepest 
abysses of the ocean. 
The great pressure to which they have 
been subjected has a curious effect on the 
deep-sea fishes when they are brought to 
the surface. Under these circumstances, 
being released from the accustomed press- 
ure, they fall to pieces, as it were. The 
eyes bulge out, the swim-bladder protrudes 
from the mouth, the scales fall off and the 
flesh comes off in patches, the tissues being 
remarkably loose. Now these fishes, dis- 
reputable as they appear when brought to 
the surface, were doubtless respectable 
enough in their proper habitat, and, like 
some other creatures, become loose and far 
from correct in appearance when away from 
home, simply because the pressure is less. 
In the depths they are doubtless no more 
conscious of the pressure of four or five 
tons to the inch than we are of the fifteen 
pounds of atmospheric pressure under which 
we live and move and have our being. 
Owing to the incompressible nature of 
water it does not differ appreciably in den- 
sity at different depths, and any object that 
will sink at the surface will continue to sink 
until the bottom is reached, however deep 
that may be. 
The presence of oxygen is of course of 
vital import to animal life in the deep sea 
as elsewhere, and it was long deemed im- 
possible that any considerable quantity of 
oxygen could exist at great depths. It has 
been found, however, that there is no lack 
of this vital element either near the surface 
or in the deepest soundings. Sir Wyville 
Thomson, the naturalist in charge of the 
Challenger, made a very careful study of 
oceanic currents and found that the cold 
water of the polar regions, charged with 
oxygen derived from the superincumbent 
atmosphere, creeps along the bottom to- 
SCIENCE. 
(N.S. Vox. XIII. No. 335. 
wards the equator from both poles, thus 
carrying oxygenated water over the vast 
area of sea bottom throughout the oceanic 
floor of the world. It also appears that 
the general trend of the surface water is 
toward the poles. This great scheme of 
circulation involves the general rise of the 
cold, deep water of the equatorial regions 
toward the surface, where it receives a 
fresh supply of heat and oxygen, carries 
much of the heat to northern regions and, 
after giving it off, returns southward again 
in the form of oxygen-bearing undercur- 
rents. To my mind there are few terres- 
trial phenomena more impressive than this 
majestic cosmic current with circulation 
slow and sure, carrying with it the tremen- 
dous potency of life to and throughout the 
uttermost depths of the sea. Were it not 
for this world circulation, it is altogether 
probable that the ocean would in time be- 
come too foul to sustain animal life, at least 
in its higher manifestations, and the sea, 
the mother of life, would itself be dead. 
The condition of the physical environ- 
ment of the life of the ocean depths that 
strikes one as the most forbidding is the 
practical absence of sunlight from the 
enormous area included in the deep sea. 
As already stated, actual experiment has 
shown that photographic plates are not 
affected at a depth of over 125 fathoms in 
clear water, and light, which can not be 
detected by the exceedingly delicate eye of 
the camera, is surely invisible to any organ 
of vision constructed on the same general 
plan as the humaneye. There is practical 
agreement among all the authorities, save 
one, that I have been able to consult 
that the rays of the sun do not penetrate 
perceptibly below the 200-fathom line at 
the farthest. Professor Verrill is the ex- 
ception referred to, and he has advanced. 
the theory that a pale green light pene- 
trates even to the deepest waters. He 
thinks that all the other colors of the spec- 
