NO. 7 SEA-LILIES AND FEATHER-STARS CLARK 2/ 



A tabulation of the colors according to depth shows that black does 

 not occur below 55 fathoms ; red, violet, gray and white do not occur 

 below 300 fathoms ; purple, green and orange do not occur below 

 600 fathoms ; yellow and brown occur at all depths. 



Yellow and brown are relatively much more frequent below 300 

 fathoms than above; purple, green, orange, gray and white occur in 

 about the same relative proportions down to 300 fathoms, at that 

 point decreasing abruptly or disappearing altogether; red, violet and 

 black decrease abruptly below 55 fathoms. 



No colors are more frequent between 55 and 300 fathoms than 

 elsewhere. The proportion of uniformly colored species increases 

 markedly with depth, while the corresponding decrease in variegated 

 species is even more abrupt. All of the color types given occur only 

 above 300 fathoms. The median dorsal stripe is most common be- 

 tween 55 and 300 fathoms. Distinctively colored pinnules and regu- 

 lar crossbands occur in about the same proportion down to 300 

 fathoms. Distinctively colored cirri and irregular spotting or mottling 

 are much more common above 55 fathoms than below. Regular 

 spotting occurs only above 55 fathoms. 



Whereas the development of color in the crinoids seems to have a 

 more or less definite relation to illumination, it appears to have no 

 relation whatever to the temperature of the water in which the 

 crinoids live. The various color types are almost entirely confined to 

 water of high or intermediate temperature ; but this is undoubtedly 

 due to the fact that the crinoids of the colder parts of the oceans 

 belong to groups in which color patterns are not developed even in 

 their tropical representatives. This supposition is emphasized by the 

 occurrence of several well-marked and beautiful color types in the 

 species of the genus Antedon which are quite as well developed in the 

 Scandinavian species as in those inhabiting the shores of northwestern 

 Africa and the Mediterranean. 



From the evidence at hand the following conclusions seem justified : 



White, which is the original color of the pentacrinoid young and 

 occurs frequently in the adults, denotes the more or less complete 

 absence of pigment. 



Yellow is the color of practically all of the more primitive forms, 

 and of many of the more specialized, throughout life, and with very 

 few exceptions (occurring in the brilliantly illuminated littoral) of 

 small specimens and of advanced pentacrinoids. Orange or red, in 

 reality an intensification of the yellow, is the color of a few primitive 

 forms, and of nearly all the young which are not yellow. 



