12 



differing from each other in those shapes, or proportional 

 lengths of parts of the body which we call morphological 

 characters, and those differences which we can observe in 

 studying samples obtained month by month from the same 

 fishery region may be due to the successive appearance of 

 the various genotypes, or to the predominance of one or more 

 of them in the samples. Further, the various genotypes may 

 respond differently to the nature of the environment, the 

 temperature and salinity of the water, or the reaction or some 

 other physical condition. In the course of the Manx summer 

 fishing, for instance, these physical conditions change markedly, 

 and so there may be successive immigrations of different 

 herrings— something like this is really what the fishermen appear 

 to think is the actual case. If so, then, it will be wrong in 

 principle to adopt a method of " lumping " together data 

 obtained from the same region in order merely to get the big 

 samples, which appear to be necessary from the statistical 

 point of view. 



It is with these considerations in mind that a critical study 

 of the methods and data of the herring race investigation has 

 been attempted by Mr. Birtwistle and Miss Lewis. 



Shellfish Investigations. 



Two troublesome questions arose in the course of the 

 administrative work of the Committee : (1) the alleged over- 

 crowding of some of the cockle beds in the neighbourhood of 

 the Dee, and (2) the pollution of the mussel beds in the estuary 

 of the Ribble. The former difficulty originated in complaints 

 made by some fishermen that the cockles on certain beds were 

 so small that most of them passed through the legal gauge. 

 This was probably the case, but the matter was not to be 

 remedied by reducing the legal size and so enabling a few men 

 to glut their customers with small cockles fetching a much 

 smaller price. In such circumstances the remedy must lie in 



