FISHES 207 



It is worth while to consider whether we can discover 

 any special reason why the definite co-operation of male and 

 female should be necessary for the fertilisation of the small 

 buoyant ova of the Dragonet, while in other cases, such as 

 that of the Cod, no such special pairing takes place. It 

 seems evident from Mr. Holt's observations, and from the 

 fact that the males are more numerous, that the milt of 

 several males is required to fertilise the ova produced by one 

 female. Each male, therefore, probably produces a very 

 small quantity of milt at a time. But this is also the case 

 in the Common Sole, in which Mr. Butler was unable to 

 detect any signs of definite pairing during spawning in the 

 aquarium. One explanation that suggests itself is, that 

 dragonets have not the habit of congregation, but live 

 scattered about at considerable intervals on the sea-bottom. 

 In that case, the quantity of eggs and milt being very small 

 in comparison to the quantity of sea -water in which a 

 number of the fish are living, the eggs would escape 

 fertilisation unless the milt and eggs were brought into 

 close proximity. Whether this is the only explanation or 

 not, the important fact in relation to the subject of the 

 present work is, that the male actually exhibits a sexual 

 excitement, under the influence of which he performs certain 

 observed movements in order to invite and attract the 

 female, and that these movements are not performed by the 

 female. 



With regard to the structural peculiarities of the male, 

 the careful observations of Mr. Holt show that each one 

 of them corresponds to a particular muscular movement 

 regularly and frequently repeated in courtship and pairing. 

 The two dorsal fins are erected, especially the front one, 

 which is so greatly elongated. This habit of erecting the 

 fins is not practised under the same circumstances by the 

 female. It is a logical inference that the special activity 



