DEPARTMENT OF MARINE BIOLOGY. 163 



The color changes of Chcetodon miliaris and Callyodon ahula are very sug- 

 gestive. The former is a yellowish butterfly-fish whose most striking marking 

 of any other color is its vertical, black, ocular band; the latter, a parrot-fish, 

 whose young, especially, appear in many color-phases. Both the yellow and 

 the black of Chcetodon fade when the fish leaves the reef and moves out over 

 pale, fine sand. The same is true when it rises a yard or more from the bottom. 

 This species is the first in which a color-change dependent upon its vertical 

 movement was definitely noted, but mature specimens of the black Das- 

 cyllus albisella were later seen putting off most of their dark color as they 

 floated higher and higher above the bit of rock or coral over which they might 

 have taken their station. So changes in coloration may occur in fishes as 

 they move from one point to another a few feet distant either in the horizontal 

 or vertical plane. But if such is the case, and if in addition the greater num- 

 ber of observed changes in coloration tend, to all appearances, to reduce the 

 visibiHty of the individuals displaying them, it seems, in view of the present 

 state of our knowledge, that the nuptial colors of fishes should possibly be 

 considered a reflection of more or less distinct and temporary change of habit 

 or habitat, rather than mere concomitants of increased vigor or products of 

 sexual selection, as many have supposed. 



Young specimens of C. ahula, about 3 inches in length, were common on 

 the reef flats at Pukoo and are notable in this connection for one thing alone. 

 As a school of these fishes passes, for example, from a bottom covered by 

 small fragments of dead gray coral to another covered by larger pieces of the 

 same material, almost all will probably turn from a mottled gray to very 

 dark brown, which at present I am obliged to interpret as a response to the 

 greater extent and intensity of the shadows beneath them in the second 

 instance. But if certain creatures are capable of masking themselves tem- 

 porarily in shadow colors, and if the ocular stripe of Chcetodon, to which refer- 

 ence has already been made, is a "shadow-picturing" mark, as it may be, it 

 seems very plausible to say that permanent dark lines, spots, or larger areas 

 in the patterns of butterflies, for example, may have the same significance. 



There is no group of animals in which species capable of changing color 

 so abound as among fishes. There is, then, no other group in respect to which 

 the biological significance of animal coloration lies so open to testing by 

 controlled observation and experiment. It is, therefore, of interest that as 

 knowledge of the color reactions of unconfined fishes continues to accumulate, 

 the interpretation which it seems necessary to place upon the color of 

 higher animals in general departs more and more widely from those generally 

 accepted. 



Studies on Alcyonaria in the Pacific Ocean, hy Lewis R. Gary. 



A. GROWTH-EATES OF SOME ALCYONARIA AT PAGO PAGO, AMERICAN SAMOA. 



The specimens of Alcyonaria of which the growth-rates were studied were 

 first measured in April 1917. All of them were left undisturbed in their 

 original location on the reefs about Pago Pago Harbor. The second measure- 

 ments were made in July 1918, so that about 15 months had elapsed between 

 the times when the two measurements were made. 



Although six species of Alcyonaria are found rather commonly on the 

 reefs about Tutuila, measurements of only four were recorded, since these 

 make up by far the most important element in the alcyonarian fauna. In 

 the order of their importance as contributors to the reef limestones in this 

 region the four species recorded are: Lohophytum (Alcyonium) rigidum Dana, 



