270 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



sample for December 17th, 1920, was composed of mussels so 

 large and well-nourished that they must have enjoyed the most 

 favourable conditions on the Skear, from which they were 

 obtained. Although such samples cause irregularities in the 

 tables showing weights and percentages, they do not obscure 

 the general trend of the figures. 



The methods of dealing with the shellfish in the laboratory 

 have already been described.* The selection of six mussels at 

 random from the whole sample, for the drying and subsequent 

 analyses, has been successful, within limits, as may be seen by 

 examination of Table I. The figures for the average weights 

 of shell and of flesh for the six mussels, and the corresponding 

 ones for the rest of the sample, do not show differences which 

 alter the main conclusions. For instance, a graph plotted for 

 the average weights of wet flesh for the rest of the sample 

 shows fluctuations, but the curve does not differ fundamentally 

 from a corresponding curve for the six mussels. 



Differences in Weight. 



The weight of wet flesh in both years rises from May, 

 with variations, to December, and then maintains a relatively 

 high value until there is a rapid fall to almost half the maximal 

 value in the April oi May of the following year. 



The series of weights given by the dried flesh show the 

 same sequence in a more marked manner. It will be seen that, 

 during one part of the year, it is possible for the mussel beds to 

 yield two-fold the amount of foodstuff that they offer at 

 another time. 



The proportion of water to dry flesh is least from August 

 to October, and shows an increase before and after spawning in 

 the Spring. There is no doubt that all these differences of 

 condition are connected directly with the reproductive cycle of 

 Mytilus. In May the mussels were in a spent condition. The 



* Report on the Lancashire Sea Fisheries Laboratory, 1920, pp. 74-84. 



