146 BULLETIN OF THE BUREAU OF FISHERIES. 



The solubilities of the pigment were then studied, using the green-gilled tissue as 

 freshly taken from the Uving oyster and the tissue after it had been thoroughly dehy- 

 drated. The gills of several oysters extracted in alcohol, 95 or loo per cent, gave a 

 slight yellowish-green coloration to the extract. A carbon disulphide extract of green- 

 gills yielded also a yellow-colored solution. But when either one followed the other 

 the second was always somewhat paler. The gills, however, always remained green 

 after such extraction, showing that the green pigment was insoluble in carbon disul- 

 phide or alcohol. White oysters yielded the same results. So it appears that these 

 extractions were merely dissolving a pigment common to any oyster gill, probably a 

 lipochrome. A yellow carbon disulphide extract was evaporated down and left a yellow 

 residue that was insoluble in water. This residue was mixed with oil and subjected to 

 the Crampton-Simon test for the detection of carotin. The result was negative. Chlo- 

 roform and ether were also turned a yellow color when used to extract the greengill, 

 but as in the case of other solvents, the extract did not differ from that obtained from 

 normal oysters. 



In dehydrating the green-gilled tissue, the following reagents were used in the order 

 mentioned : Alcohol, ether, and carbon tetrachloride. This method always left the car- 

 bon tetrachloride sUghtly yellow colored and gave a dark green residue of dried gill 

 tissue. This dehydrated tissue was then ground and used in solubility tests that fol- 

 lowed. The solvents in different strengths of alkaU and acid were used, with the following 

 results : 



ALKALI. . 



0.1, 0.2, 0.3, 0.4, 0.6, 1.2, 1.5,3, and 6 per cent potassium hydroxide; no pigment dissolved. Material 

 from greengill swelled up into a flocculent gelatinous mass with unchanged color. The supernatant 

 fluid gave an opalescent appearance, but there was no solution of the pigment. 



12, 30, and 60 per cent potassium hydroxide; decomposed green-gilled material, leaving a greenish- 

 brown residue. 



The same results were detected when the solutions were kept at room temperature 

 during 24 hours- or when boihng solutions were used during short periods. 



o.oi, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.2, 2, 2.5, 3, and 3. 5 per cent hydrochloric acid; no action noticeable. 

 4, 7, and 15 per cent hydrochloric acid; slight yellowish-green coloration, but green-gilled material 

 remains tmchanged. 



18 per cent hydrochloric acid; disintegrated tissue and turned black. 



In the last four strengths of acid recorded, probably disintegration was taking 

 place, while actual dissolving of the original pigment did not occur. 



The above results on acids were detected when the solutions were either hot or cold, 

 or when the pigment was allowed to remain in the solution for a period of 24 hours. 

 The same results were observed when alkalies were used. Hot or cold water did not 

 dissolve the green pigment. 



After the pigment had been shovm to be insoluble in the common solvents, experi- 

 ments were undertaken to ascertain if there was any chemical combination of the 

 pigment with a protein or fat molecule. In the investigation on this point, green-gilled 

 tissue was subjected to a gastric digestion first, by putting several gills into a 0.2 per 

 cent acid solution of pepsin and allowing the digestion to go on for three days at 37° C. 

 On the third day the digestion was examined, and a small amount of green material was 



