DEPARTMENT OF MARINE BIOLOGY. 201 



nesce when lucif erase is added, while a control tube kept in darkness shows no 

 trace of luciferin. The action is more marked with the ultra-violet, as a solu- 

 tion of oxyluciferin in a quartz tube showed more reduction than one in a glass 

 tube when exposed for the same length of time to the quartz-mercury arc. 

 The reduction is not dependent on the formation of acid under the influence 

 of Ught, since two tubes of oxyluciferin, one kept in darkness and the other 

 exposed to sunlight for 6 hours, had the same reaction, Ph = 9.3. Of course, 

 some reducing substance might be formed under the influence of Hght, but 

 this is not very probable. 



We may therefore write the reaction for luminescence in Cypridina in the 

 following way: 



darkness 



alkali 



luciferase 

 luciferin (LH2)+0^l2:oxy luciferin (L)-t-H20 (luminescence) 



perhydridase (a reducing enzyme) or nascent H 



acid 



Hght 



Report of Additional Observations and Experiments upon Problems of 

 Animal Coloration, by W. H. Longley. 



The interval between June 5 and July 3, 1919, was spent at Tortugas in 

 continuation and extension of my previous investigation in the field of animal 

 coloration. For the privilege of continuing my work for a time after the formal 

 closing of the Laboratory I am particularly grateful. 



Attention has been called in a previous report to several pairs of closely 

 related species in which a specific sort of difference in coloration is correlated 

 with a definite difference in behavior. Abudefduf sordidus and Chromis 

 elaphrus are bottom-haunting Hawaiian fishes of dusky or yellow-ohve shades, 

 without trace of the blue or blue-gray which is so conspicuous an element in 

 the coloration of A. abdominalis and C. ovalis. The two species last named 

 habitually swim high in the water, where their blue-gray pigments reduce 

 their visibihty from the point of view of an observer at a lower level. 



In this connection it is interesting to note that the same difference in be- 

 havior occurs in the case of Abudefduf taurus and A. saxatilis, which are quite 

 similar in appearance to A. sordidus and A. abdominalis respectively, and, in a 

 sense, replace them in the Tortugas fish fauna. Teuthis hepatus and T. 

 cosruleus are Ukewise a pair of related species in which the predominantly 

 olivaceous and blue types of coloration appear in correlation with the specified 

 difference in habit. 



These facts simply emphasize the general conclusion that the interpreta- 

 tion to be placed upon the color of animals should be sought through study in 

 detail of their relation to their environment. 



Regarding the significance of pattern, the most suggestive observation made 

 during the summer referred to the squid, Sepia sp. 



The coloration of this small cephalopod, hke that of some others at least, 

 is almost incredibly fluid. It is now dark brown, now exceedingly pale; now 

 longitudinally striped, now transversely banded. One does not encounter 

 the creatures frequently under water, but one at least of their changes in 

 appearance occurs so regularly that it requires only a few moments to de- 

 termine the system followed. When swimming, the squid is longitudinally 

 striped; when, except for the rippling motion of its lateral fins, it is at rest, 

 it is transversely banded. Tliis, however, is exactly the rule wliich certain 

 fishes follow, which, like the squid, have alternative striped and banded color 

 phases. 



