162 CARNEGIE INSTITUTION OF WASHINGTON. 



menesema, agree with their West Indian relatives in feeding by night and 

 hiding in coral or rock crevices during the day. The red color of this group 

 is correlated, then, both in the Atlantic and in the Pacific, with the habit of 

 living in dim light. 



It is interesting to note in this connection that Pseudupeneus porphyreus 

 and Mulloides auriUamma, two of the Mullidge which feed by night and school 

 about rocky cavernous places by day, have each a red phase which they 

 assume when they pass from the open into the deep shadow under over- 

 hanging ledges. On the other hand, A. menesema, which is more retiring, has 

 a gray phase which I have seen it display when near the bottom over bare 

 sand in the mouth of a small cave, while other individuals higher up in the 

 shadow were reddish brown. It may be noted incidentally that the visibility 

 of this color is very low under the conditions stated, much lower than yellow, 

 for example. For a fish strongly marked with yellow may be seen far back 

 in the cavern, when a red one much nearer at hand and almost in the direct 

 line of vision may be perceived with the greatest difficulty. 



Julis gronovii seems an exception to the general rule that there are no truly 

 red fishes of the shallower tropical waters which are not nocturnal, for in 

 spite of its clearly defined wliite markings it is largely of a vivid red color 

 which it has no evident power to suppress under any condition. It is of 

 interest, then, to note that this is apparently the young of /. pulcherrima, 

 for all intermediate forms between the two ai'e seen upon the reefs, but not 

 so commonly that it was possible to secure a series for the purpose of making 

 the point absolutely certain. However, little is left to be desired when in 

 individuals scarcely beyond arm's reach one may see that the characteristic 

 markings of gronovii become fainter and fainter as the fishes increase in size, 

 while one after another of the distinctive features in the coloration of pul- 

 cherrima comes into being until the perfect form is attained. The transforma- 

 tion is no greater and the stages in the transition no less easy than in the case 

 of Thalassoma hifasciatus and T. nitidus, to which attention has been called 

 in a previous report. So it still seems probable that in spite of the compara- 

 tively common occurrence of a red coloration among fishes, diurnal species 

 whose red is of more than a transient character are almost or quite absent 

 from shallow tropical waters. 



Hawaiian fishes possess to a marked degree capacity to change their colora- 

 tion as their surroundings or their activities vary; 27 species, representing 22 

 genera and 9 families, were observed to alter color in one or more respects 

 as their relation to their environment changed. To these should perhaps be 

 added 5 others concerning which the evidence is not quite so clear; 22 of 

 the 27 effected adjustments in shade; 13 changed their pattern; and 11 

 changed their color in a definite manner under stated conditions. 



Transverse bands or longitudinal stripes may distinguish alternative color- 

 phases of a single species. When such is the case the banded pattern tends 

 to mark fishes resting near the bottom and the striped one those in motion. 

 Though Coris venusta, Pseudupeneus pleurostigma, and P. porphyreus show 

 comparable changes, this is most clearly illustrated among Hawaiian fishes 

 by Cheilio inermis, in the coloration of which gray, brown, olive, and yellow 

 replace one another from moment to moment as these colors happen to pre- 

 dominate in its environment; and if one has a score of specimens under 

 observation at once in theii* brown phases in a sargassum patch, it is very 

 clear that each momentary pause or trifling advance is closely followed as 

 a rule by the change from stripes to bands, or vice versa. Self-color phases, 

 however, may also appear during motion and are of hues dependent upon 

 the color of the smToundings. 



