The problem of the generation of eels is one of the most abstruse and
curious in natural history; but we have been much pleased, and not a
little enlightened, by some observations on the subject in Sir Humphrey
Davy's delightful little volume, _Salmonia_, of which the following is
the substance:--
Although the generation of eels occupied the attention of Aristotle, and
has been taken up by the most distinguished naturalists since his time,
it is still unsolved. Lacepède, the French naturalist, asserts, in the
most unqualified way, that they are _viviparous_; but we do not remember
any facts brought forward on the subject. Sir Humphrey then goes on to
say--This is certain, that there are two migrations of eels--one up and
one down rivers, one _from_ and the other _to_ the sea; the first in
spring and summer, the second in autumn or early winter. The first of
very small eels, which are sometimes not more than two or two and a half
inches long; the second of large eels, which sometimes are three or four
feet long, and which weigh from 10 to 15, or even 20 lbs. There is great
reason to believe that all eels found in fresh water are the results of
the first migration; they appear in millions in April and May, and
sometimes continue to rise as late even as July and the beginning of
August. I remember this was the case in Ireland in 1823. It had been a
cold, backward summer; and when I was at Ballyshannon, about the end of
July, the mouth of the river, which had been in flood all this month,
under the fall, was blackened by millions of little eels, about as long
as the finger, which were constantly urging their way up the moist rocks
by the side of the fall. Thousands died, but their bodies remaining moist,
served as the ladder for others to make their way; and I saw some
ascending even perpendicular stones, making their road through wet moss,
or adhering to some eels that had died in the attempt. Such is the energy
of these little animals, that they continue to find their way, in immense
numbers, to Loch Erne. The same thing happens at the fall of the Bann,
and Loch Neagh is thus peopled by them; even the mighty Fall of
Shaffausen does not prevent them from making their way to the Lake of
Constance, where I have seen many very large eels. There are eels in the
Lake of Neufchatel, which communicates by a stream with the Rhine; but
there are none in the Lake of Geneva, because the Rhone makes a
subterraneous fall below Geneva; and though small eels can pass by moss
or mount rocks, they cannot penetrate limestone rocks, or move against a
rapid descending current of water, passing, as it were, through a pipe.
Again: no eels mount the Danube from the Black Sea; and there are none
found in the great extent of lakes, swamps, and rivers communicating with
the Danube--though some of these lakes and morasses are wonderfully
fitted for them, and though they are found abundantly in the same
countries, in lakes and rivers connected with the ocean and the
Mediterranean. Yet, when brought into confined water in the Danube, they
fatten and thrive there. As to the instinct which leads young eels to
seek fresh water, it is difficult to reason; probably they prefer warmth,
and, swimming at the surface in the early summer, find the lighter water
warmer, and likewise containing more insects, and so pursue the courses
of fresh water, as the waters from the land, at this season, become
warmer than those from the sea. Mr. J. Couch, in the Linnaean
Transactions, says the little eels, according to his observation, are
produced within reach of the tide, and climb round falls to reach fresh
water from the sea. I have sometimes seen them in spring, swimming in
immense shoals in the Atlantic, in Mount Bay, making their way to the
mouths of small brooks and rivers. When the cold water from the autumnal
flood begins to swell the rivers, this fish tries to return to the sea;
but numbers of the smaller ones hide themselves during the winter in the
mud, and many of them form, as it were, masses together. Various authors
have recorded the migration of eels in a singular way; such as Dr. Plot,
who, in his History of Staffordshire, says they pass in the night across
meadows from one pond to another; and Mr. Arderon, in the Philosophical
Transactions, gives a distinct account of small eels rising up the
flood-gates and posts of the water-works of the city of Norwich; and
they made their way to the water above, though the boards were smooth
planed, and five or six feet perpendicular. He says, when they first
rose out of the water upon the dry board, they rested a little--which
seemed to be till their slime was thrown out, and sufficiently
glutinous--and then they rose up the perpendicular ascent with the same
facility as if they had been moving on a plane surface.--There can, I
think, be no doubt that they are assisted by their small scales, which,
placed like those of serpents, must facilitate their progressive motion;
these scales have been microscopically observed by Lewenhoeck. Eels
migrate from the salt water of different sizes, but I believe never when
they are above a foot long--and the great mass of them are only from two
and a half to four inches. They feed, grow, and fatten in fresh water.
In small rivers they seldom become very large; but in large, deep lakes
they become as thick as a man's arm, or even leg; and all those of a
considerable size attempt to return to the sea in October or November,
probably when they experience the cold of the first autumnal rains.
Those that are not of the largest size, as I said before, pass the
winter in the deepest parts of the mud of rivers and lakes, and do not
seem to eat much, and remain, I believe, almost torpid. Their increase
is not certainly known in any given time, but must depend upon the
quantity of their food; but it is probable they do not become of the
largest size from the smallest in one or even two seasons; but this, as
well as many other particulars, can only be ascertained by new
observations and experiments. Block states, that they grow slowly, and
mentions that some had been kept in the same pond for fifteen years. As
very large eels, after having migrated, never return to the river again,
they must (for it cannot be supposed that they all die immediately in
the sea) remain in salt water; and there is great probability that they
are then confounded with the conger, which is found from a few ounces to
one hundred pounds in weight.
* * * * *
At Munich, every child found begging is taken to a charitable
establishment; the moment he enters his portrait is given to him,
representing him in his rags, and he promises by oath to keep it all his
life.
* * * * *