448 
TUBE-BLADDERED GR 0 UP. 
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 iidand 
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 
