208 



considerHtioii ;^^)cs, it was centred round the ninntli of April. 

 The fall in weight in the October and November of both 

 years might suggest sporadic spawning during these months, 

 especially as in one or two cases the mantles showed little 

 difference in thickness from those of a spent " fish " (0-7 — 0-8 

 mm.). This thinness, however, was due to poor condition ; the 

 mantle consisted of coimective tissue, and a few immature eggs 

 or sperm sacs, and did not show the typical collapsed con- 

 ditioji containing but a few residual ripe reproductive elements, 

 which one associates with a spawned mussel. 



The dift'erences in the weight and condition of the samples 

 for April and May in f92f show that a short and thorough 

 spawning had taken place between these two months. The 

 spring of f922 exhibits a less well-defined spawning period. 

 One or two mussels of the March sample ran with spawn Avhen 

 being handled. Millions of fry had settled on the Morecambe 

 8kears in mid- April, which (if the estimation that it takes 

 about a month for the larvae to settle down* is reliable) 

 suggests spawning in March and possibly in February. 



The April sample also showed a condition where some 

 nmssels were full and others not, and it was only after 

 examination of some shellfish sent in May that one felt sure 

 the spawning period had come to an end. 



Proteid. 



'i'lie ii.ni()unts o[ proteid Jiave been obtained by multiplying 

 the Kjeldhaj nitrogen values by the usually accepted factor 

 0*25. This assumes molluscan proteid to be the same in 

 empirical composition as that of the higher animals, and must 

 therefore be adopted with some reservation. Factors obtained 

 from the amount of nitrogen in fat-glycogen-ash-free substance 

 give somewhat higher values, but they vary, and the experi- 

 ments cannot be regarded as definitive. Whatever factor is 



* Johustoiie, ibid., p. 38. 



