566 W. H. LONGLEY 



dus foetens lies flat, and may sink with one convulsive wriggle 

 till only the dorsal surface of its head — or nothing — is visible 

 beyond the depression beneath which it is buried. Flounders 

 too, when resting, commonly bed themselves and diminish their 

 visibility. In these various species each reaction, though their 

 result be one, is performed in distinctive fashion. 



The Labrids commonly use the pectorals alone in swimming, 

 but when they are about to bury themselves, all their trunk and 

 tail muscles are called into play, and in an instant they plunge 

 head foremost out of sight. That the behavior of three genera 

 should be consistent each with the other, and yet be without 

 observed parallel beyond the family, is significant. The ex- 

 pedition with which the reaction is carried out, its regular re- 

 currence at nightfall, the ease with which it may be evoked 

 at any time of day by darkening the tank, and a tendency to 

 perform it at a stated time, even in the absence of essential 

 conditions, are also significant, for all alike emphasize its habitual 

 character. Unfortunately it has not been noted in nature, but 

 as that might occur only through some lucky accident, there can 

 be little doubt that it is a normal response of the animals, and 

 explains, at least in part their nightly disappearance. 



The Chaetodons, Angel fish and Tangs are diurnal. The most 

 interesting record concerning them in the table is that regarding 

 Pomacanthus arcuatus. This shows that in the very long in- 

 testine of some fishes that ingest great quantities of food during 

 the day much may remain many hours later. What may fix 

 their feeding time, is not the presence or absence of material in 

 the alimentary tract, but its apparent freshness. The grouped 

 observations upon these fishes are consistent with the idea that 

 they feed by day. They fit in well with what has been noted of 

 their diurnal activities, and the fact that at night they are not 

 on the open reef, but are more or less definitely sheltered among 

 the heads. 



It does not appear that the activity of all fishes varies so dis- 

 tinctly at different times. The yellow-tail and red grouper seem 

 to feed when food is available, and to be governed by no other 

 condition. From superficial agreement in habit with Epine- 



