species, though
the water twice every year becomes perfectly evaporated, and the mud of
the bottom becomes converted into dust, or takes the condition of baked
clay, gaping with wide and deep clefts, in which not the slightest sign
of moisture can be detected. This is the case with temporary hollows in
the soil, which have no connexion with running streams or permanent
waters, from which they might be supposed to receive a fresh stock of
fish.

Two modes of accounting for this strange phenomenon have obtained
currency. The one is that received by those Europeans who are content
with any solution of a difficulty, without too closely testing it; viz.,
that the fishes fall with the rains from the air. The actual occurrence
of such showers rests, as we have just seen, on good evidence; but,
admitting the fact, it must be a rare phenomenon, whereas the presence
of fish in the new-made pools is universal. Again, if the rains brought
them in such abundance as to stock all the pools, an equal number would
fall on the dry ground, which is not pretended to be the case. The other
accepted solution is that which has received the sanction of Mr Yarrell,
who observes--"The impregnated ova of the fish of one rainy season are
left unhatched in the mud through the dry season, and from their low
state of organisation _as ova_, the vitality is preserved till the
occurrence and contact of the rain and the oxygen of the next wet
season, when vivification takes place from their joint influence."[79]

This may be fully allowed, yet it does not meet the exigences of the
case. Sir E. Tennent and others have shewn that it is not young fishes
just escaped from the egg which appear in the new-formed pools, but
full-grown fishes, fit for the market; a fact well known to the
Singalese fishermen, who resort to the hollows as soon as the monsoon
has brought rain; and they invariably take in these pools, which a day
or two before were as dry as dust, plenty of fishes fully grown, a foot
or eighteen inches long, or longer.

Neither of these hypotheses, then, will account for the fact: and we
must admit that the fishes of these regions have the instinct to burrow
down in the solid mud of the bottom, at the approach of the dry season,
and the power of retaining life, doubtless in a torpid condition, until
the return of the periodic rains, as Theophrastus long ago observed.[80]

The _Lepidosiren_, a very remarkable genus of animals from Africa and
Sout