292 



A HISTORY OF FISHES 



taken by the parents. A female Carp [Cyprinus] of four pounds 

 weight has about four hundred thousand eggs, one of sixteen 

 and a half pounds more than two million. The relations 

 between the sexes in the breeding season may be described as 

 polyandrous, for, although in certain species pairing may take 



Fig. 1 06. 



Breeding-grounds and distribution of the European Fresh-water Eel {Anguilla 



anguilla) and the American Eel {Anguilla rostrata). 

 The continuous curved dotted lines show the limits of occurrence of the larvae 



(the European species represented thus , the American species thus 



). In the case of the European Eel, that marked 10 embraces an area that 



must include the actual spawning places of the species, for within it larvae less 

 than 10 millimetres in length have been captured in large numbers, but never 

 outside it. The numbers on the other curves denote the length of the larvae in 

 millimetres captured therein. The adults of the European species occur in the 

 countries outlined with short horizontal lines, those of the American species in 

 the regions shovv^n by dots outside the coast line. 



place, in the majority each female is attended by two, three, 

 or even more males, all of which take part in the fertilisation 

 of the eggs when extruded. As a rule, the males develop hard, 

 wart-like, nuptial tubercles at this season, which may be confined 

 to the head or extend on to the skin of the back and sides. 

 These excrescences, disappearing as soon as spawning has been 



