156 



BULLETIN OF THE BUREAU OF FISHERIES. 



glycogen content. The great variations in ash percentages are due not only to the differ- 

 ences in density of water, but also to variations in the amount of sea water included in the 

 shell contents used for analysis. The metabolic changes in glycogen, therefore, are more 

 fairly represented by the percentages in the ash-free solids than by those in the total 

 solids of the oyster. It apparently makes no difference whether the oysters at the start 

 contain much or little glycogen. The amount formed in any case is about the same for 

 two or three days' treatment with dextrose, i. e., 1.5 to 2.5 grams of glycogen to every 

 100 grams of organic matter. The numbers of oysters used in these experiments would 

 seem to exclude the possibility of accounting for variations by mere individual differ- 

 ences, especially since the dried shell contents of all oysters used in any one experiment 

 were very thoroughly ground and mixed before analysis. 



The storage of glycogen can not continue indefinitely under the adverse conditions 

 used in these experiments. In one case oysters kept in aerated but unchanged sea 

 water, containing 0.25 per cent of dextrose, during five days, yielded glycogen to the 

 amount of 1 1 . 1 2 per cent of the ash-free solids, but the corresponding figure for some of 

 the same oysters analyzed at the beginning of the experiment was 13.57 per cent. 



Further experiments to test this point were made as shown in Table 3. 



Table 3.- — Effect of Varying Durations of Dextrose Feeding on Glycogen Formation. 



Treatment of oysters (15 used for each analysis). 



In aerated sea water containing K per cent dextrose during 20 hours 



Same as No. 25 but continued during 44 hours. 



Same as Nos. 25 and 26 but continued during 6S hours 



From same lot as Nos. 35. 26, and 37, analyzed as a control 



Analyzed at beginning of experiments Nos. 30 to 34 as a control 



In aerated sea water containing \4 per cent dextrose, i day 



Same as No. 30, 2 days, water ( ' 4 per cent dextrose) renewed second day . . , 

 Same as Nos. 30 and 31, 3 days, water (K per cent dextrose) renewed daily 



Same as No. 32. 4 days 



Same as No. 33, 5 days 



From same lot as Nos. 29 to 34 analyzed at end of No. 34 as control 



Ash in 

 dried 

 meats. 



Per cent. 



32.17 

 31- 12 

 30- 3 S 



34-40 



25.56 

 33-46 

 31. 22 

 39.8s 

 30.60 

 29-50 



34.70 



Glycogen 

 in dried 

 meats. 



Per cent. 

 6.07 

 S-i6 

 4-34 



4.84 



3-74 

 5.06 

 6- II 

 4-68 

 5-03 

 4.89 



396 



Glycogen 

 in ash- 

 free 



solids. 



Per cent. 

 8.94 

 7-49 

 6.23 



7-39 



S-OI 

 7-60 

 8.87 

 6.68 

 7-25 

 6.97 



6.06 



These experiments show that the maximum glycogen formation under these cir- 

 cumstances occurs in about two days. Although in experiments Nos. 30 to 34 the water 

 containing dextrose was daily renewed and constantly aerated, yet glycogen did not show 

 a progressive daily increase. The control oysters (experiment No. 29) were analyzed imme- 

 diately after they were brought from the beds at Wareham, Mass. There the specific 

 gravity of the water is lower than at Woods Hole. This explains why the second set of 

 control oysters (experiment No. 35), analyzed after remaining five days in Woods Hole 

 water, gave a higher ash yield than the first lot (experiment No. 29), though taken from the 

 same beds at the same time. What effect this may have had on glycogen formation is 

 discussed later. That the oysters of experiments No. 31 to 34 did not have as high an ash 

 content as those of No. 35 may indicate a failure to remain open and feed continuously 

 under the experimental conditions. With smaller concentration (o.i per cent) of dex- 

 trose, glycogen formation may continue for three days. (See experiments Nos. 37 and 

 38, Table 4.) 



