2820 



THE BONY FISHES AND GANOIDS 



fish leave rivers and brackish waters for the sea, their reproductive organs have 

 scarcely begun to develop. But their maturing in the sea must be rapid, because 

 in five or six weeks they have arrived at a breeding condition. This rapidity of 

 maturing in the breeding organs would seem to be the cause of extreme exhaustion. 

 Consequently, after the breeding season is over, eels die, similarly to lampreys, and 



EELS IN THE MUD. 

 (One-eighth natural size.) 



several other piscine forms; and this furnishes the explanation why, subsequent to 

 this period, old eels are not observed reascending rivers." After describing the 

 appearances of the reproductive organs in fully- developed eels of both sexes, as well 

 as those of sterile individuals, Day observes that " it becomes necessary to allude to 

 the localities in which each of these forms may be found. Here, again, imagina- 

 tion seems to have mixed up fact with fiction, and it has been maintained that 



