SEA-FISHERIES LABORATORY. 269 



SEASONAL CHANGES IN THE CHEMICAL 

 COMPOSITION OF THE MUSSEL {MYTILUS EDULIS). 



(Continued). 



By R. J. Daniel, B.Sc. 



The investigation into the seasonal variations in the flesh 

 of Mytilus edulis, which was referred to in last year's Report on 

 the Lancashire Sea Fisheries Laboratory, has now been con- 

 cluded, and covers a period of two years. Observations show 

 a marked annual reproductive cycle which, on the whole, 

 repeats itself in each of the two years. The discrepancies are 

 probably due, in the main, to the unavoidable errors of 

 sampling. 



The data obtained from examination of the samples, 

 tabulated in various ways, is shown in the attached tables. 

 It is not possible just yet to publish the results obtained from 

 microscopic sections, stained to show the distribution of fat and 

 glycogen in the tissue, but since the information obtained from 

 these latter investigations is closely bound up with the fluc- 

 tuations in chemical composition, it will be necessary to refer 

 to it in passing. 



The samples sent from Morecambe are to some extent 

 " selected " mussels. They have been gathered in the same 

 manner as the fishermen pick them for food, only those greater 

 than two inches (5-1 cms.) being taken. This is not altogether 

 a disadvantage ; it lessened the irregularities with regaid to the 

 size of the mussels, and allows of results which are comparable 

 with the shellfish that are actually put on to the market. 

 Most of the mussel samples showed an average length of 

 6-0 — 6-5 cms., and only five of them averaged so low as 

 5-5 — 6-0 cms. There were one or two samples which were 

 obviously not in the " general " run. For example, the mussels 

 received on August 16th, 1921, were small, and with very 

 dark shells ; they were procured from a bed near to Morecambe, 

 and not from the usual Skears. On the other hand, the 



