S4 
IOWA ACADEMY OF SCIENCES. 
(h) Reds, yellows and greens predominate. 
(c) These colors are in masses, usually in striking con- 
trast. 
(cl) Commensal associations of similarly and brilliantly 
colored animals are frequent. 
II. As to physical conditions: 
(a) Great pressure. 
(b) Uniform low temperature. 
(c) Practical absence of sunlight. 
(d) Aggregation of animals in limited areas. 
(e) A considerable amount of organic matter near the 
bottom. 
III. As to visual organs among deep-sea animals: 
(a) They are possessed by a majority of animals that 
normally possess them in shallow water. 
(b) They are often of great size among deep-sea forms. 
(c) They are often, on the other hand, either rudimentary 
or aborted. 
IV. As to jjhosphorescent light: 
(a) It is found among practically all classes of deep-sea 
forms. 
(b) It is often of remarkable brilliancy. I, myself, have 
seen it so brilliant, on the surface of course, that 
ordinary print could be read from the deck of a 
vessel. 
(c) It is possessed by animals that are known to be aggre- 
gated in immense quantities at certain spots 'at the 
sea bottom. 
(d) It has the remarkable actinic property of rendering 
particularly conspicuous the reds, yellows and 
greens.'^' 
Here, then, it would seem that we have a light that would 
render the characteristic colors of deep-sea animals, i. e., the 
reds, yellows and greens, conspicuous, and no less nor more 
explicable than similar colors among their shallow- water rela- 
tives. In many cases they are doubtless to be regarded as 
warning coloration, as in the sea urchins, whose sharp spines 
are frequently banded with brilliantly contrasted red and 
*Mosely found that the phosphorescent light emitted by certain marine forms 
consisted of red, yellow and green rays only, and adds: “Hence, were the light in the 
deep sea derived from this source, in the absence of blue and violet, only red, yellow 
and green colors could be effective.” (Quoted from Agassiz’ “Three Cruises of the 
Blake,” p. 310.) 
