IOWA ACADEMY OF SCIENCES. 27 



be seen that we, too, were foundation builders, that upon our 

 work has risen a temple of science commensurate in useful- 

 ness, beneficence and inspiration, with the imperial destiny of 

 oui; 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 ia 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 eifects 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 my own observations, 

 most of whicli are recorded in my narrative 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 ccelenterata appear to be 

 the groups which are most prolific in such coloring matter. 

 Pentocrinin and antedonin seem to be widely difl'used 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 diifused, abundant and 



'Quarterly Journal of Microscopical Science, xvil, p. 1. 



