212 



tissue of the body and mantle, in the muscle, and even the 

 labial palps and gills, yet it has not been possible to get the 

 same staining reactions in the " liver " itself. This means 

 that if there is glycogen present in the organ, it is either there in 

 such a form or in such minute quantities that methods which are 

 successful for the demonstration of it in other parts of the body 

 are unable to detect it in the liver. 



In this concentration of glycogen in the connective tissue, 

 as well as in the slowness of inversion in the body, Mytilus 

 seems, to contrast markedly with the oyster. Mitchell* states 

 that in the latter mollusc, glycogen is found mainly in the liver 

 region. In the Report of the Government Chemist for the 

 year ended 31st March, 1921, page 24, it is stated that deter- 

 mination of the glycogen in oysters was " carried out with 

 difficulty owing to its rapid change to other carbohydrate 

 matter immediately after opening the oyster." 



In the light of this evidence it is interesting to compare 

 the seasonal variations in carbohydrates of the mussel described 

 above, with the quantity of glycogen present in samples of 

 oysters examined throughout the year by J. A. Milroy.f 

 Speaking of the percentages of dry glycogen in the moist animal, 

 Milroy says : "As regards seasonal variations there is a 

 gradual rise in the percentage from the beginning of August 

 until the middle or end of October. This is succeeded by a fall 

 which reaches its minimum about the middle of December. 

 From that period onwards the percentage rises until it reaches 

 its maximum some time between the beginning of April and 

 early in May. The percentage then falls until it reaches its 

 second minimum early in August." 



According to Bulstrode,J oysters in British waters spawn 



* MitcheU, Bull. Bureau of Fisheries, U.S.A., XXXV., 1915-16, p. 483. 



t Milroy, " Seasonal variations in the quantity of Glycogen present in 

 samples of Oysters." Dept. of Agriculture and Technical Instruction for Ireland 

 Fisheries Branch Sclent. Investigation, 1907, No. IV. 



X Bulstrode, 24th Annual Report of Local Govt. Board, 1894-95. Supple- 

 ment, " On Oyster Culture in relation to Disease," p. 8. 



