182 CARNEGIE INSTITUTION OF WASHINGTON. 



end of the experiment, instead of several times during starvation. Thus 

 these medusae received less severe treatment in the course of the experiment 

 than those previously studied. 



All the cassiopeas here used were dried at a temperature of 80° to 90° C. 

 for a week and then later dried at the Wistar Institute under better laboratory- 

 conditions. The object of this was to determine the water-content as well as 

 the nitrogen-content of the dried substance before and after starvation. 



Since the present work is still incomplete, I am unable to make any state- 

 ment concerning the detailed results, and therefore I shall limit myself to 

 two general conclusions: 



(1) The rate of the reduction in body-weight during starvation is nearly 

 identical in both the present and the previous study (1916). It appears, 

 therefore, that whether starvation is performed on the entire or on the half 

 body the results are similar, so far as the rate of reduction is concerned. 



(2) The water-content of the body was identical in both the starved half and 

 the control half, both giving on the average 94.94 per cent. 



An attempt was made to determine the growth of Cassiopea in weight and 

 in the diameter of the disk in respect to age. For this purpose 9 small cassi- 

 opeas, ranging in body-weights from 0.12 to 1.20 grams, were placed in a wire 

 cage, the bottom of which had been covered with coral sands taken from the 

 place where the cassiopeas were abundant. This wire cage was submerged 

 in the lagoon of Garden Key, on the collecting-ground of the medusae. Unfor- 

 tunately a storm which occurred 10 days after this experiment was started 

 washed away the cage and the cassiopeas were lost. It was determined, 

 however, that cassiopeas made an average of 31 per cent increase in body- 

 weight at the end of one week. 



A second experiment was begun, using cassiopeas of different sizes, also 

 placed in a wire cage in the lagoon. However, the location this time was 

 evidently not suited to their growth, though the place was perfectly safe from 

 storm, and so two weeks later the medusae were found to have lost in body- 

 weight to the extent of 20 per cent on the average. Thus these studies ended 

 in failure. The problem of the body-growth in respect to age is fundamentally 

 important, and it is therefore the hope of the present writer to be able to pursue 

 this study at some future time. 



Report of Observations and Experiments upon the Biological Significance of 

 Animal Coloration and an Extension of the Field of Color-Photography, by 

 W. H. Longley. 



In continued prosecution of studies previously reported, I worked at 

 Tortugas from June 8 to August 13, 1917. During that time effort was 

 expended upon three undertakings: (1) to secure photographs of fishes in 

 different color phases and engaged in different characteristic activities noted 

 in preceding seasons; (2) to test the possibility of demonstrating by color- 

 photography to what extent their colors repeat those of their environment; 

 (3) to determine the meaning of certain variations in color which I had 

 ob.served earlier in Brachyura. 



In the attempted achievement of the first two objects the essential appa- 

 ratus consisted as before of a submarine camera and diving hood. A 4 by 5 

 Auto-Graflex replaced the No. Graphic camera used during the preceding 

 summer. This was fitted with a Bausch & Lomb, Tessar lens, series Ic, f . 4. 5, 

 suitable for an instrument taking a plate 5 by 8 inches in size. Its container 

 was water-tight, neither excessively large nor heavy, and so could be carried 

 about conveniently upon the bottom. By means of plungers and screws 



