IOWA ACADEMY OF SCIENCES. 
27 
be seen that we, too, were founclath)!! builders, that upon our 
work has risen a temple of science commensurate in useful- 
ness, beneficence and inspiration, with the imperial destiny of 
our river-bordered state. 
THE COLOR OF DEEP-SEA ANIMALS. 
BY C. C. NUTTING. 
The purpose of this paper is to explain the phenomena of 
bright colors among marine animals living in the sea beyond 
the depths to which sunlight can be supposed to penetrate to 
such an extent as to render bright colors visible. Although 
there are doubtless actinic effects of sunlight at considerable 
depths, we are safe, I think, in saying that colors cannot be 
clearly distinguished at a depth greater than 100 fathoms. 
Photographic experiments show that the ‘‘extreme limit 
of effect of the sun’s rays on sensitive plates is at a depth of 
250 metres,” or less than 125 fathoms. As to the facts con- 
cerning coloration of deep-sea animals — and the deep sea may 
be considered from our standpoint as any depth below 100 
fathoms — all our information leads to the conclusion that the 
phenomena of bright colors are present in all groups The 
main sources from which I have drawn this conclusion are the 
“Challenger” Reports and Narrative, “The Three Cruises of 
the Blake, ” by Alexander Agassiz, and mj^ own observations, 
most of which are recorded in my narratwe of the “Bahama 
Expedition ” sent out by the State University of Iowa. Pro- 
fessor Mosely, of the Challenger staff, says: ''' 
“Peculiar coloring matters giving absorption spectra have 
now been found to exist in all the seven groups of the animal 
kingdom. The echinodermata and coelenterata appear to be 
the groups which are most prolific in such coloring matter. 
Pentocrinin and antedonin seem to be widely diffused in 
immense quantities through the tissues of the crinoids in which 
they occur; and the echinoderms generally seem to be charac- 
terized by the presence of evenly diffused, abundant and 
^Quarterly Journal of Microscopical Science, xvil, p, 1. 
