448 TUBE-BLADDERED GROUP. 



generally of smaller size than the females, have been recognised. " For the 

 generation of eels it would seem, so far as we are at present aware, that the 

 presence of salt water is a necessity, for it has been observed that when these 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 

 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, 

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

 that should very young eels be introduced from the mouths of rivers into inland 

 pieces of water, they invariably develop into fish of the female sex, as it was 

 supposed males were never to be seen in fresh water. Whether such waters are 

 really conducive to the destruction of young male eels, appears to be a subject 

 requiring further elucidation. The female eels are those usually captured when 

 descending towards the mouths of rivers during the autumn months, while such 

 as are developing towards a breeding condition do not seem to feed at these 

 periods. Males have been usually obtained from the mouths of rivers or in 

 brackish waters ; and Dr. Paul, having discovered that among elvers, or young 

 eels, captured in such localities were males, ascertained (at least so he asserts) that 

 when transported to fresh waters, they retained their masculine character, develop- 

 ing into adults. Some have been captured ten or twelve miles up rivers ; but, 

 although male eels undoubtedly ascend rivers, their proportionate number to that 

 of females decreases in accordance to the distance from the sea. Sterile eels are 

 found in fresh waters, and likewise in those which are brackish, where they may 

 often be captured feeding, but these fish, of course, cannot increase in numbers 

 unless they have access to the sea, and consequently above impassable barriers 

 they die out, should no young be introduced. The migrations of these fishes may 

 be said to be two annually, adults descending seawards to breed, as they do in the 

 Severn, about the month of September, although this migration in Norfolk is 

 asserted to begin as early as July. There is likewise an up-stream migration of 

 young eels, or elvers, in the earlier months of the year up to May or June, or even 

 later ; during this period the banks of the rivers being in places black with these 

 migrating little fishes. These young eels have been observed to ascend floodgates 

 of lochs, to creep up water-pipes or drains ; in short, mechanical difficulties scarcely 

 obstruct them, and they will even make a circuit over a wet piece of ground in 

 order to attain a desirable spot." In order to give some idea of the vast numbers 

 of young eels that take part in these migrations, or, as they are popularly called 

 ' : eel-fares," it may be mentioned that upwards of three tons of elvers were dis- 

 patched in a single day from the Gloucester district in the spring of 1886, and 

 that it has been calculated that over fourteen thousand of these fish go to make a 

 pound weight. In the previous year the annual consumption of eels was estimated 



