FISHES OF THE DEEP-SEA 
By L. Hussakof 
P TO the time of the “ Challenger” 
expedition, little 
known regarding the fish life 
of the abyssal depths of the sea. Only 
about thirty species were known. But 
the wonderful collections brought back 
by the “Challenger” 
WEY Was 
four- 
year cruise (1873-1876) made known 
from her 
the vast diversity, the strangeness and 
even weirdness of this fish fauna. Sev- 
eral hundred kinds of deep-sea fishes 
had been collected —some of them 
dredged from a depth of more than a 
mile — and it required a huge quarto! 
to describe and picture them. From 
this volume dates our real knowledge 
of the fishes of the abyssal deep. The 
“Challenger” expedition was, indeed, a 
“Columbus voyage” in ichthyology; 
it opened a new chapter in the history 
of the science. 
Since that time many deep-sea ex- 
ploring expeditions have been sent out 
by the various nations, and hosts of 
other fishes have been brought up from 
the oceans in all parts of the world. 
More than a thousand species are now 
known, and we can appreciate at its full 
value the 
this faune 
know the 
richness and strangeness of 
Moreover, not only do we 
fishes themselves, but as a 
result of the scientific investigations 
carried on by the various expeditions, 
we now know a good deal of the physical 
conditions under which they live, so 
that we can, in a measure at least, ex- 
plain the why and wherefore of their ex- 
traordinary characteristics. 
When we think of life in the deep-sea, 
there comes to mind, first of all, the 
enormous pressure which these creatures 
must withstand. This pressure becomes 
1 Challenger Reports, Vol. XXII, 1887. 
the greater the deeper we go down, and 
in the profoundest depths it equals thou- 
sands of pounds to the square inch. The 
result of this pressure is that the tissues 
of these fishes are tender and loosely 
knitted together. When they 
brought up out of the dark depths, and 
are 
the great pressure under which they live 
is removed, the explosion of the gases 
within them bulges out the eyes, and 
often blows out the viscera through the 
the collapse, 
leaving them soft and flabby like moist 
mouth, while muscles 
rags. Most deep-sea fishes are very 
small also, usually only a few inches in 
length, and it is probable that this re- 
duction in size has come about to some 
extent at least, from the great pressure 
under which they live. 
Another important condition is the 
dimness of light, or even darkness in the 
profound depths of the sea. If we im- 
agine ourselves descending into the deep 
ocean, we see the light grow dimmer and 
dimmer as we go down, until finally a 
level is reached beyond which no light 
penetrates at all. The entire vast depth 
below it, is in eternal darkness. Now 
the fishes living in this dim light, or in 
total darkness, have been profoundly 
modified by it. In some forms the eyes 
have become very small, and in some 
cases have entirely disappeared. There 
are even fishes in which the skin and 
scales of the body have grown over the 
place where the eyes should be, so that 
these fishes are, as has been aptly said, 
“blind Other 
forms, on the other hand, have been 
affected in an entirely different way. 
The eyes, instead of growing smaller, 
have grown larger, as if in an attempt to 
catch every fleeting ray of light. In 
249 
beyond redemption.” 
