28 NORTH SEA INVESTIGATIONS. 



IV. On the Relations of the Generative Organs and of the 



Sexes in Some Fishes. 



Althouijli a considerable number of observations have been made 

 and published concerning the sizes of ripe, nearly ripe, and spent 

 fish, and on the condition of the reproductive organs in these 

 various stages, we are far from possessing at present a complete and 

 satisfactory knowledge of the changes through which these organs pass 

 in the development of the fish to maturity, and from one spawning 

 period to the next. This is in fact a subject where investigation re- 

 quires minute microscopic study, and the application of advanced 

 microscopical science ; and the investigation is necessarily an extended 

 one, because it involves a complete examination of all stages in a given 

 fish, and a comparison of all the different fishes with one another. 

 I have a few observations and suggestions to offer here in addi- 

 tion to those contained in my papers on the subject in previous 

 numbers of this Journal. 



The first point I wish to consider is the remarkable difference in pro- 

 portional size between the ovaries and testes in different species, and in 

 relation to this, the differences between the sexes in number and size. 

 To Dr. Fulton belongs the credit of having first drawn attention to these 

 phenomena, and he has published some important data concerning 

 them, and suggested some explanations. (See his papers in the 8th, 

 9th, and 10th Eeports of the Scottish Fishery Board). It is well 

 known that in some fishes, as in the herring, the testes or soft roes are 

 as large as the hard, and the same is true of Clupeoids generally. In 

 the cod family it is difficult to judge without accurate weighing, but the 

 testes, which are of a curious frilled shape, quite different from that 

 of the ovaries, do not appear obviously smaller than the latter. In the 

 flat-fishes, on the other hand, the testes are always smaller than the 

 ovaries, and the minimum is reached in the sole, where they are so 

 small as to have been formerly entirely overlooked. Dr. Fulton has 

 given the actual weights of the organs in a number of specimens, but 

 has not worked out the proportion they bear to the weight of the fish. 

 From averages of 10 male herrings and 16 females it was found that in 

 fish of 11"2 in. in length the testes weighed 35'6 grammes, the ovaries 

 35"0, so that the testes were actually a little heavier. In a male cod 

 39 in. long the ripe testes weighed 846 grammes, while in a female of 

 38 in. the ovaries weighed 2,124 gms., or more than twice as much. A 

 difficulty in exact comparison arises from the varying conditions of the 

 organs, whether in the development towards maturity, or whether the 

 discharge of products after spawning has commenced ; all that can be 

 done is to compare them just before the commencement of spawning. 



