NUTRITION OF oysters: NATURE OF THE "FATTENING" OF OYSTERS. 481 



Table 2. — Comparison op Glycogen and Nitrogen of Oysters which Show Sudden Changes 

 IN Glycogen Due to Abnormal Feeding Conditions. 



Experi- 

 ment 



No. 



Treatment. 



Glycogen 



content. 



Fed dextrose 



do 



Fed chopped seaweeds 



Starved in filtered water 



Starved in partly purified water. . 



Fed dextrose 



do 



do 



In polluted water 4 days 



Changed from salt to fresh water . 

 In polluted water 14 days 



Ash-free solids. 



Per cent. 



14.76 



14. 61 



14. 22 



13-91 



13-51 



8-94 



8.83 



7-63 



6. 23 



S-S9 



3-05 



Nitrogen 

 content. 



Nitrogen 



in ash- 

 free and 

 glycogen- 

 f ree solids. 



Per cent. 



69 



Per cent. 

 13-15 

 12.94 

 12-95 

 13-35 

 12.81 

 12.75 

 12.92 

 13- 16 

 13.40 

 12.84 

 13.09 



Changes in the proportion of protein present, aside from the uniform increase due to 

 growth, no doubt occur in the oyster. An instance is shown by examination of certain 

 of these results. Those in Table 3, chosen because they represent analyses made very 

 soon after the oysters were taken from their natural habitat, show marked differences 

 in their nitrogen content. This is true even when figured on a glycogen-free basis. That 

 seasonal changes are responsible for this is indicated by the fact that oysters taken in 

 July and August, which include the spawning season, tend to show a higher proportion 

 of nitrogen than those taken in November. Further work would be required to give an 

 adequate explanation of this, but the suggestion that accumulation of egg and sperm 

 materials, together with heightened metabolism of reproductive glands, may be the 

 explanation is obvious. 



Table 3.- 



-Comparison of Glycogen and Nitrogen op Oysters which Had Not Been Subjected 

 TO Abnormal Experimental Conditions. 



Experiment No. 



4.. 

 16, 

 18, 



Date 

 when 



taken 

 from 

 water. 



Nov. 15 

 Nov. 15 

 Aug, 20 

 Aug. 7 

 Aug. 10 

 July 7 



Ash-free solids. 



Glycogen 

 content. 



Per cent. 



22. $2 

 21.65 

 14.89 

 II. II 

 9-63 

 7.29 



Nitrogen 

 content. 



Per cent. 

 8.86 

 9.87 

 II- 20 

 12. 24 

 12. 22 



Nitrogen 

 in ash-free 



and gly- 

 cogen-free 

 solids. 



Per cent. 

 11.46 

 12. 60 

 13-17 

 13-76 

 13-53 

 13-17 



Experiment No. 



25 

 26 

 27 

 29 



Date 



when 

 taken 

 from 

 water. 



July 27 



July 29 



July 19 



July 20 



July 22 



Ash-free solids. 



Glycogen 

 content. 



Per cent. 

 7.09 

 6.49 

 6.40 

 5-86 

 5-64 



Nitrogen 

 content. 



Nitrogen 

 in ash- 

 free and 

 glycogen- 

 free solids. 



Per cent. 

 62 

 17 

 24 

 12 



Per cent. 



12.54 

 13-00 

 13-08 

 12.79 

 12. 73 



VARIATIONS OF FAT IN THE OYSTER COMPARED WITH THOSE OF GLYCOGEN. 



The storage of fat in oysters, as detected by ether extraction of the dried meats, was 

 also investigated. In the previous paper ° the suggestion that fat might be formed from 

 dextrose was tentatively made. It was based, however, on only two experiments and 

 is not substantiated by the results of 13 analyses reported in Table 4 below. These later 



o Bull., Bureau of Fisheries, vol. xxxv, 1915-16, pp. 155-161 



