Physiological Changes with Age in Fish 



205 



the exponent lying between 0-5553 and 0-6035. Thus, the 

 number of eggs does not increase in proportion to the weight 

 of the ovary (Fig. 2). 



Plaice is the fourth species to show this peculiar relationship. 

 It had also been reported by Hickling in the English herring, 

 by Raitt in haddock and by Bagenal in the long rough dab. 



SOOr 



240 



180 



120 



60 



• ^ •• • 



• •• 



PLAICE 



60 120 180 



OVARY WEIGHT IN GRAMS 



300 



Fig. 2. Scatter diagram of the relation between fecundity 



and ovary weight in the plaice (Pleuronectes platessa). 



From Simpson (1951). 



The explanation for it is still in doubt, but a clear-cut problem 

 has emerged. A choice can be made between Bagenal's inter- 

 pretation that larger ovaries may produce larger but fewer 

 eggs, and Hickling' s tentative conclusion that connective 

 tissue may increase disproportionately in the ovaries of older 

 fish. The decision can be made by studying the histology of 

 the ovary, provided a method can be devised for measuring 



