48o 



BULLETIN OF THE BUREAU OF FISHERIES. 



protein, etc., in oysters to express results in terms of percentage content of the ash-free 

 solids. Glycogen and nitrogen, the latter to be used as an index of the amount of 

 protein, were determined in many specimens of oysters of varying nutritive conditions. 

 Some oysters were analyzed immediately after removal from their natural habitat, 

 others after treatment in various artificial ways. 



The results of a series of analyses are given in Table i. The arrangement is in 

 decreasing order of the amounts of glycogen in the ash-free solids. 



Table i. — Comparison of the Glycogen and Nitrogen Content op Oyster Meats. 



Examination of Table i shows that as the percentage of glycogen in the ash-free 

 solids decreases the percentage of nitrogen, similarly computed, tends to increase. 

 There is not a regular mathematical relationship between the two sets of figures, but 

 many of the irregularities would fall within the limits of experimental errors. At 

 any rate, the series shows strikingly that protein, as indicated by nitrogen determina- 

 tions, does not increase in oysters as an accompaniment to glycogen storage. 



In spite of their long continued growth, oysters, indeed, have some tendency 

 toward nitrogen equilibrium. Like the higher animals, oysters not only store glycogen 

 in preference to protein when food is plentiful, but also use glycogen to protect them- 

 selves from loss of body protein when food is scarce. Evidence of this is shown by a 

 more detailed examination of some of the results recorded in this table. Eleven of 

 these results are segregated in Table 2. They were selected because in each case pre- 

 vious experiments, recorded in the first paper" of this series, showed that changes in 

 glycogen amounting to 10 per cent or more had occurred in periods from 2 to 14 days. 

 The various abnormal feeding conditions causing these sudden fluctuations in glycogen 

 content are explained in Table 2. 



That the comparatively small variations in the nitrogen percentages in ash-free 

 solids are merely due to the glycogen fluctuations can be seen from the computations 

 of the percentage of nitrogen figured not only on an ash-free but also glycogen-free 

 basis. These results are sufficiently uniform to show that sudden variations in the 

 food supply of oysters are not accompanied by changes in their protein content. 



o " Nutrition of oysters: Glycogen formation and storage, " Bull. Bureau of Fisheries, vol. xxxv, 1915-16, pp. 151-161. 



