146 STUDIES IN INSECT LIFE, ETC. 



(5) We have found that the sexes of the plaice 

 have a different rate of growth, a different size 

 and age on attaining reproductive maturity, a 

 different rate of mortality, as well as differences 

 in their distribution and in the extent and range 

 of their migrations. Starting life in approxi- 

 mately equal numbers, the females outnumber 

 the males by about three to one when seven 

 years old, and by about ten to one above that 

 age. The majority do not attain maturity until 

 between five and six years of age in the case of 

 females, and between four and five years of age 

 in the case of males. At different times of the 

 year the sexes segregate and are unequally subject 

 to the liability of capture by the fishermen. 



The bearings of such facts as these on the 

 diagnosis and treatment of the problems of 

 over-fishing are too manifest to require elabora- 

 tion. 



(6) We have investigated the feeding habits of 

 the plaice, and the extent to which their growth 

 is dependent upon the temperature of the sur- 

 rounding sea and the character of the sea bottom. 



(7) By experiments on the transplantation of 

 young plaice from their nurseries in the coastal 

 waters on to the rich food ground of the Dogger 



