IOWA ACADEMY OF SCIENCES 29 



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 Luidia was a rich chocolate 

 with conspicuous white spines. Among the sea urchins may 

 be noted a Coefoj)Ieun<s with crimson and white spines, a Salenia 

 with vermilion and white barred spines, an Aspidocliadeitia 

 with spines banded with purplish velvet and white, a very 

 brilliant (heloplouriis 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 eoncerniag physical conditions are taken from 

 The Three Cruises of the Blake," Agassiz, chapter xiii. 



