211 



parable, but the former was found to be the shorter, and easier 

 of manipulation. The results obtained are given as percentages 

 in Tables III and IV, and in all cases but one fall below the 

 corresponding figures for the carbohydrates calculated by 

 difference. These differences cannot be due entirely to the 

 wrong use of a constant (such as the proteid 6-25, or that of 

 0-927 used for calculating glycogen from glucose) because they 

 vary in amount. 



As seen above, there is no sign of the discrepancy being 



due to inversion into glucose, before the samples were tested 



for glycogen, and this is borne out by sections, which show 



great quantities of glycogen, even when the tissue is not fixed 



until it arrives at the laboratory. It may be that there is some 



non-nitrogenous, organic matter present which exists in other 



forms than glycogen and its inverts. This is at once the most 



interesting, but, so far, the least conclusive part of the whole 



investigation. One fact which is of importance, however, 



emerges from the data, and that is that both the relative 



amounts of glycogen and carbohydrates by difference are 



at a maximum, on the whole, about October, and then decrease 



rapidly to immediately before the spawning time. This 



decrease in glycogen before the time of spawning is of additional 



interest when one studies its distribution in the tissues of the 



animal. MacMunn* was unable to discover glycogen in 



sections of the digestive gland of several invertebrates, including 



Mytilus edulis, and the study of sections of one or two mussels, 



fixed in absolute alcohol on the mussel beds, as well as that of 



many sections made from mussels after having been received at 



the laboratory, has led to the same conclusion. In all sections, 



whether from mussels fixed directly or after they have been 



on a railway journey, it has been possible to detect glycogen by 



staining with iodine and Best's Carmine after several fixatives, 



in changing quantities throughout the year, in the connective 



* Phil Trans., 1887, part I, p. 257. 



