NORTH SEA. INVESTIGATIONS. 29 



In a male plaice 21 in. long the testes weighed 29"5grms. ; in a female 

 23| ins. the ovaries weighed 503 grms. In the lunipsucker, in a male 

 12 in. long the testes weighed 70'8 grms., in a female 17 in. long 

 the ovaries weii^hed 878 crrms. 



If the small size of the testes were compensated by the greater 

 abundance of the males, an approach to equality in the quantity of the 

 generative products might be the result. But the opposite of this, 

 according to Dr. Fulton's researches, is usually the case. Thus in the 

 cod there were found to be 133 females to 100 males, in the plaice 142 

 females to 100 males, but in the lumpsucker there were only 25 

 females to 100 males, and in the herring the numbers of the two sexes 

 were very nearly equal. Dr. Fulton considers the probable significance 

 of these relations, and concludes that the testes are usually smaller in 

 fish with pelagic ova, and more nearly equal in those with adhesive ova, 

 and he thinks the explanation is that fertilisation is more certain in the 

 case of pelagic ova, because the sperms move upwards like the eggs, 

 while in the case of attached ova a great deal of the milt is wasted. 

 There is probably much truth in this suggestion, but I would put it in 

 a somewhat different way. In the sea the water is generally moving in 

 one direction or another, and the milt shed into the water disperses by 

 diffusion, even without the movement of a current. Therefore, if the 

 eggs are fixed, much of the milt must travel away from them, and 

 more of it is required. Where the eggs are free in the water like the 

 milt, they scatter together, and are moved together by the currents. It 

 is remarkable, however, that in the angler, of which the eggs, though 

 free in the water, remain connected in a continuous sheet, the males are 

 much more numerous (100 males to 26 females), and the males are also 

 larger, though whether the testes are larger than the ovaries has not 

 been ascertained. 



But the proportion in bulk between testes and ovaries differs very 

 greatly among fishes which agree in having pelagic ova. For instance, 

 in the cod the inferiority of the testes is very much less than in the 

 plaice, and in the plaice than in the sole, while in the flounder, although 

 the testes are smaller, the males are more numerous than the females. 

 It seems to me that these differences are to be explained by the 

 differences in the rate of spawning. Some fishes, like the herring, shod 

 the whole crop of eggs for the season at once. The eggs are all in the 

 same stage of development, and therefore are all ripe at one time, and 

 when spawning begins it continues at a rapid rate until the roe is 

 empty, and the fish is spent. Plaice and cod do not spawn so rapidly 

 as this, but it is certain that in both these fishes a large number of eggs 

 can be squeezed from a ripe female at one time, so that the roe is soon 

 emptied. The rate of spawning, and its duration, can be studied by 



