766 



REPORT — 1892. 



new crop of ova commences to mature as soon as, or even before, the old crop has 

 been ejected. Moreover some of the old ova are invariably retained in the ovary, 

 and their presence is perceptible even several months after spawning. In some 

 species, also, the ovary, on maturing, grows backwards, and thus assumes new 

 topographical relations which it never again entirely loses. 



It has been suggested that confusion may occur between immature females and 

 females in which the ovaries, having once fulfilled their function, have reverted to 

 a condition of rest. I can find no evidence that the latter condition is ever 

 realised — at all events amongst marine Teleosteans. 



In distinguishing immature females from such as are just commencing to 

 approach ripeness, I find the most easily recognised microscopical feature in the 

 relative translucency or opacity of the ovum. 



In immature fish the condition and size of the ova are not materially influenced 

 by the size of the individual in any species, but at the first approach of sexual 

 activity an opacity manifests itself, under the microscope, in certain of the ova, and 

 brings about changes in the appearance of the ovary, which, after some experience, 

 are easily recognisable by the naked eye. 



The changes in the ovum which bring about this opacity are familiar to students 

 of ovarian development. 



]\Iale fish being of comparatively small importance in the present connection I 

 have not devoted much attention to the minute anatomy of the testis, but it 

 presents certain well-marked external characteristics which serve to distinguish 

 the different conditions. 



The table of comparative size-limits suggests a close relationship between the 

 absolute size of a species and the size at which maturity is attained by that species 

 in difterent districts. 



Rate of growth being doubtless related to absolute size, it must be presumed, 

 in view of Cunningham's researches, that there is a constancy in the age at which 

 maturity is reached in all districts. 



Most of the observations embodied in the tables were made during the spawning 

 season. 



Extracted feom ti[e Tables. 



Smallest ripe male 

 9 inches. 



Common Sole. 



Ijargest immature male 



11 inches. 

 Largest immature ^ 



12 inches. 



ISmallest ripe female 

 lOi inches. 



Smallest ripe S 

 12 inches 



Turhot. 



Largest immature S 

 11 inches. 



Smallest ripe 

 18 inches. 



Largest immature % 

 19 inches. 



Smallest ripe S 

 12 inches. 



Brill. 



Largest immature <? 

 14 inches. 



Smallest ripe 9 

 15 inches. 



Largest immature 



18 inches. 



Smallest ripe <? 

 6 inches 



Plaice. 



Largest immature <? 

 15 inches. 



Smallest ripe ? 

 13;j inches. 



Largest immature 

 19 inches. 



Smallest ripe S 

 6 inches 



Lemmi Sole. 



Largest immature S 



8 inches 



Smallest ripe <^' 

 10 inches. 



Largest immature V 

 12 inches. 



