186 SEXUAL DIMORPHISM 



authors have described the violent rushes and leaps of male 

 Cyprinoidfl when spawning is about to take place. Fatio 

 writes of the common freshwater bream, Abramis brama. as 

 follows : " Les jeux de l'amour de ce Cyprin sont excessive- 

 ment tapageurs, et Ton entend souvent de tres loin le vacarme 

 que font a la surface les bandes de Bremes dans leur delire 

 amoureux. Ce sont des courses effrenees, des contorsions 

 varices, de puissants coups de queue lances en tous sens, et 

 des baisements a fleur d'eau. Plusieurs males poursuivent 

 generalement une seule femelle." It is not evident from 

 this that the males intentionally push each other with their 

 heads, but in such manoeuvres they must be continually 

 striking their heads against each other, or against the females, 

 or against the weeds, and Lunel, 1 in the case of Alburnus 

 lucidus and other species, speaks of the rubbing of the fish 

 against each other. On the other hand, the tubercles are 

 not described as present in the Tench, and this fish performs 

 its spawning quietly. In most species of the family the 

 males are distinguished by an enlargement, or swelling, of 

 the anterior rays of the pectorals, especially in the spawning 

 season ; in the Tench by a thickening of the second ray of 

 the pelvic fin. These modifications also are doubtless due to 

 special exertions of the organs. 



Murcenidw. In the Mursenidae the chief sexual difference 

 is the small size of the male in comparison with the female. 

 Whether this is true throughout the family I do not know ; 

 I am only able to give particulars concerning the two British 

 species, the Conger and the Freshwater Eel. No male congers 

 have been described which were more than 2 feet 6 inches in 

 length, and the weight of the largest would scarcely exceed 

 1 lb. Females, on the other hand, frequently exceed 5 feet 

 in length, and one has been recorded which measured 8 feet 

 3 inches in length, and weighed 128 lbs. Specimens weigh- 



1 Poissons du bassin du Leman, Geneve, 1874. 



