SOUTHWELL : REPRODUCTION OF THE EEL. 



221 



their exterior appearance with a considerable degree of certainty. It 

 had not escaped the keen observation of Darwin that the male of 

 nearly all fish is smaller than the female, and Dr. Jacoby found that 

 the eel formed no exception to this rule, the female reaching a 

 considerably larger size than the male is known to attain. This 

 circumstance alone misled those who were searching for the male of 

 the eel, as it was thought that the larger the fish the greater would be 

 the probability of its organs being fully developed ; the large females 

 were thus actually selected, to the exclusion of the smaller males. 

 Dr. Jacoby also found that in the male eel the snout is more pointed; 

 the back dark green, almost black ; and the sides invariably show a 

 metallic glitter. The dorsal fin is also lower than in female eels of 

 corresponding size, and as a rule, although not invariably, the eyes 

 in the male are largest. Of the female eel he describes minutely two 

 varieties : first, the fully developed female, which migrates to the sea 

 in autumn, and which during its migration, hke the male, takes no 

 food ; and secondly, the barren female, which ' never migrates to the 

 sea, and feeds all the year round.' The latter is probably the form 

 known in our fisheries as the broad-nosed eel or ' Gloat,' which feeds 

 ravenously, but is never taken in the fixed nets, as it does not 'run'; 

 the former is probably the ' silver belly ' of our fishermen, which is 

 seldom or never taken by a bait, but on its passage to the sea is 

 intercepted by the fixed engines of the eel-fisher. 



' Drawing,' as he says, ' rational conclusions from our present 

 knowledge of the eel question,' a brief summary only of which we 

 have been able for want of space to give, Dr. Jacoby arrives at the 

 following conclusions : — 



( 1 ) ' For the development of their organs of generation , eels need salt- 

 water. As has now been ascertained beyond a doubt, the eels leave the 

 rivers and brackish lakes when their organs of generation have scarely 

 begun to develop, and enter the sea that these organs may there reach 

 their full development. That this migration to the sea is undertaken 

 for the purpose of spawning is fully proved by the fact that in spring 

 the young eels come from the sea, and this view is further strengthened 

 by the circumstance that when the eels commence to migrate they 

 cease to eat, just like other fish do, during the spawning season.' 



(2) 'The development of the organs of generation takes place in 

 the sea, not near the coast, but farther out in deep water. Considering 

 the immature condition of the eels when they begin to migrate, the 

 development is exceedingly rapid. In a few (five or six) weeks they 

 reach maturity, according to the time when they enter the sea. Near 

 Comacchio the eels migrate from the beginning of October till the 

 end of December.' 



May 1885. . V ,;:- . L 2 



