SEA-FISHERIES LABORATORY. 253 



So far, only plaice have been studied by the methods 

 of this and the previous papers. There is no reason why 

 other species inhabiting the Lancashire Fishery Area 

 should not also be investigated in the same manner. But 

 the difficulty of obtaining 1 series of data, and results 

 capable of exhibiting the relationships expected on 

 a 'priori grounds, much less capable of withstanding 

 statistical tests, is so great that only this fish has been 

 examined. It may also be expected that the results 

 obtained from the study of one species would possess a 

 certain degree of generality, and that conclusions so 

 obtained might be extended to other species. An 

 indubitable numerical correlation between physical 

 changes and plaice migrations, or rate of growth, or the 

 value of the length-weight coefficient, or the incidence 

 and duration of a spawning season, might also be 

 expected to hold good with respect to other fishes, such as 

 the sole. There would be some differences, of course, but 

 these could be allowed for by investigation of these other 

 species, on a scale of less magnitude than that applied to 

 the plaice. 



