IOWA ACADEMY OF SCIENCES 
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abounded in deep water near Havana. One ophiurian was 
brown, conspicuously marked with white, others were marked 
with purple and deep violet. The simple-armed basketfish 
were bright yellow, or bright yellow barred with brown, or 
deep orange and rich chocolate. A Luiclia was a rich chocolate 
with conspicuous white spines. Among the sea urchins may 
be noted a Godoj)leurus with crimson and white spines, a Salenia 
with vermilion and white barred spines, an AsjndocUaclema 
with spines banded with purplish velvet and white, a very 
brilliant Coeloplourus with spines barred carmine and white 
and a test with alternating chocolate and orange zones, an 
Echinus with a beautiful green test ornamented with white 
diamond- shaped patterns. The coelenterates tell the same 
story; gorgonidae of brilliant crimson, orange, yellow and 
scarlet, corals red and pink and rose color and bright yellow 
plumularian hydroids. 
The following general statements seem to me to be justified 
concerning the coloration of the animals of the deep sea: 
First. — The coloration is fully as brilliant as in shallow 
water, although perhaps not so varied. 
Second — The reds, orange, yellows, violet, purple, green 
and white predominate. 
Third. — The colors, when they occur at all, are apt to be in 
solid masses in striking contrast, or the whole animal is of a 
uniform brilliant coloration. Fine patterns are very scarce 
and nature seems to have used a large brush in adorning her 
children of the depths. 
Fourth. — There is a conspicuous absence of blue color among 
all groups. But two exceptions, a sponge and crab, have 
been noted. 
A brief reference to the physical conditions of the deep sea 
is necessary to the proper understanding of the discussion in 
the latter part of this paper.* These conditions are: 
First . — Great pressure, which of course increases with the 
depth. At a depth of 1,000 fathoms, the pressure is one ton to 
the square inch, a pressure 120 times greater than that to 
which we are subjected; while at 3,000 fathoms, the pressure 
is equal to that of 400 atmospheres Curiously enough, this 
enormous pressure does not seem to greatly affect the animals 
subjected to it. The bodies of many of them are composed 
* Most of the data in this paper concerning physical conditions are taken from 
“ The Three Cruises of the Blake,” Agassiz, chapter xiii. 
