364 NORTH SEA INVESTIGATIONS. 



pt. 4, 1892, p. 418), that any biological definition of mature and 

 immature fish must depend upon the conditions of the larger sex, or, 

 strictly speaking, upon the sex in which, as regards dimensions, 

 maturity is most retarded. This sex is almost invariably the female. 



But it must be borne in mind that when a ripe or nearly ripe fish 

 is caught there is, and I think can be, no means of determining 

 whether it is spawning for the first time or has spawned in previous 

 years. Consequently observations made during or shortly before 

 the spawning season yield results that are only entirely reliable for 

 the time of year during which they were made — for this reason, that 

 a fish which by a narrow margin was either too young or too small, 

 or from whatever cause was unfitted to spawn last season, will have 

 very materially increased in length before the present season. In 

 this connection researches on the rate of growth are of the 

 highest importance, and without a greater knowledge on that sub- 

 ject than we already possess, it is impossible to form reliable 

 conclusions. Much, however, may be done by continuing the 

 examination of the reproductive organs throughout the year. 



I do not know whether it will ever be practicable to utilise the 

 evidence afforded by such fish in formulating any size limit for 

 practical use. In any case the season is not sufficiently advanced 

 for their consideration, and therefore in the tables which are 

 appended I have only dealt with fish taken during, shortly before, 

 or shortly after the spawning season. I believe that the size 

 limits deduced from these will be quite as high as any that are 

 likely to be acceptable, and that they will be sufficiently efficacious 

 for the upkeep of the species. 



The term "immature " is used in this paperto denote that the repro- 

 ductive organs show no sign of activity, and to the best of my know- 

 ledge have not subserved a reproductive function in previous years. 



Method of distinguishing the Different Conditions. — I have studied 

 the conditions of the female reproductive organ with much more 

 attention than has been devoted to that of the male, since the 

 larger size and numerical preponderance render the former sex 

 infinitely the more important in the present connection. In the 

 case of the male I have relied chiefly on the external cha- 

 racters of the testis, viz. those of size, contour, and apparent 

 consistency, since these seem to be sufficient for the purpose, except 

 in the case of the sole, which has required more careful attention 

 than the rest. 



In the immature female, the ovary, so soon as it is large enough 

 to be easily perceptible, is found to contain a number of minute 

 translucent ova, their size and condition depending neither upon the 

 season of the year nor upon the size of the fish. Thus there is no 



