DEPARTMENT OF MARINE BIOLOGY. 173 



below the eye. The conjunctiva is also spotted in such a way that no matter 

 in what direction the eye may be rolled, with exposure of surface normally 

 hidden, the movement is not betrayed by display of surface differing in color 

 or pattern from that of contiguous areas. The spots on the dorsal surface of 

 the eye agree in size with those nearest them, while ventrally it is marked with 

 larger blotches comparable with those upon the cheek. This is a striking 

 example of consistency in detail, which is common in the field of animal 

 coloration. 



Thalassoma nitidus and T. nitidissima are now recognized as alternative 

 phases of one species, but this summer, for the first time, it became clear that 

 the predominantly yellow nitidissima phase is shown chiefly by fishes near the 

 bottom, and the slaty-blue striped or banded phase by such as swim well 

 above it. Repeatedly schools of 2 dozen or more fishes in the nitidus colora- 

 tion passed over almost instantaneously to the nitidissima type when they 

 dashed down to the bottom to feed upon a broken sea-urchin, and underwent 

 the reverse change at once when they returned to their original position. 



Fragmentary as they are in themselves, such observations as these supple- 

 ment others already on record, and it is hoped that they may at last serve 

 to give such an intimate view of the lives of fishes as might not be secured 

 elsewhere than in the tropics and under such favorable working conditions as 

 prevail at Tortugas. 



Study of the Blood of the Tortugas Crawfish, Panulirus argus, and an Analysis 

 of the Blood of a Nurse Shark, by Sergius Morgulis. 



In an earlier investigation (J. Biol. Chem. 50, 2, 1922) the writer examined 

 the non-protein constituents of the blood of several marine arthropods. The 

 data suggested a possible connection between the composition of the blood 

 and the nutritive condition of the animal, and further study of the question 

 along this line seemed necessary. The analyses have also shown that creati- 

 nine was completely absent in the arthropod bloods. This observation, how- 

 ever, was directly contradictory of certain published data, and it was there- 

 fore one of the principal objects of the investigation at Tortugas to settle this 

 matter by an intensive study. 



The blood of normal crawfish, examined practically as soon as caught, 

 had the composition shown in the table on the following page and ex- 

 pressed as usual in milligrams per 100 c. c. blood. 



After the crawfish remain in the live-car for one day practically all the non- 

 protein constituents of the blood become greatly reduced in amount. 



The relation of the changing composition of the blood and the nutritive 

 condition of the animals has been studied more directly by examining the 

 blood from the same crawfish several times in succession. This may be done 

 with the crawfish because of the relatively large amount of blood which 

 these crawfish contain and the apparent ease with which they recuperate 

 after a bleeding operation. Judging by the amount of blood obtained at 

 successive bleedings, these animals must restore their blood volume with 

 comparative rapidity. The results found for the same animal during 44 

 hours are given on the following page. 



