They Were More Than A
Yard In Length, And Diverged In An Ascending Direction From
The Orifices.
The spider then suddenly let go its hold of the
post, and was quickly borne out of sight.
The day was hot
and apparently calm; yet under such circumstances, the
atmosphere can never be so tranquil as not to affect a vane so
delicate as the thread of a spider's web. If during a warm
day we look either at the shadow of any object cast on a
bank, or over a level plain at a distant landmark, the effect
of an ascending current of heated air is almost always evident:
such upward currents, it has been remarked, are also
shown by the ascent of soap-bubbles, which will not rise in
an in-doors room. Hence I think there is not much difficulty
in understanding the ascent of the fine lines projected from
a spider's spinners, and afterwards of the spider itself; the
divergence of the lines has been attempted to be explained, I
believe by Mr. Murray, by their similar electrical condition.
The circumstance of spiders of the same species, but of
different sexes and ages, being found on several occasions at
the distance of many leagues from the land, attached in vast
numbers to the lines, renders it probable that the habit of
sailing through the air is as characteristic of this tribe, as
that of diving is of the Argyroneta. We may then reject
Latreille's supposition, that the gossamer owes its origin
indifferently to the young of several genera of spiders:
although, as we have seen, the young of other spiders do
possess the power of performing aerial voyages. [7]
During our different passages south of the Plata, I often
towed astern a net made of bunting, and thus caught many
curious animals. Of Crustacea there were many strange
and undescribed genera. One, which in some respects is
allied to the Notopods (or those crabs which have their
posterior legs placed almost on their backs, for the purpose
of adhering to the under side of rocks), is very remarkable
from the structure of its hind pair of legs. The penultimate
joint, instead of terminating in a simple claw, ends in three
bristle-like appendages of dissimilar lengths - the longest
equalling that of the entire leg. These claws are very thin,
and are serrated with the finest teeth, directed backwards:
their curved extremities are flattened, and on this part five
most minute cups are placed which seem to act in the same
manner as the suckers on the arms of the cuttle-fish. As
the animal lives in the open sea, and probably wants a place
of rest, I suppose this beautiful and most anomalous structure
is adapted to take hold of floating marine animals.
In deep water, far from the land, the number of living
creatures is extremely small: south of the latitude 35 degs.,
I never succeeded in catching anything besides some beroe,
and a few species of minute entomostracous crustacea.
In shoaler water, at the distance of a few miles from the
coast, very many kinds of crustacea and some other animals
are numerous, but only during the night. Between latitudes
56 and 57 degs. south of Cape Horn, the net was put
astern several times; it never, however, brought up anything
besides a few of two extremely minute species of Entomostraca.
Yet whales and seals, petrels and albatross, are exceedingly
abundant throughout this part of the ocean. It has always
been a mystery to me on what the albatross, which lives far
from the shore, can subsist; I presume that, like the condor,
it is able to fast long; and that one good feast on the carcass
of a putrid whale lasts for a long time. The central and
intertropical parts of the Atlantic swarm with Pteropoda,
Crustacea, and Radiata, and with their devourers the flying-
fish, and again with their devourers the bonitos and albicores;
I presume that the numerous lower pelagic animals
feed on the Infusoria, which are now known, from the
researches of Ehrenberg, to abound in the open ocean: but
on what, in the clear blue water, do these Infusoria subsist?
While sailing a little south of the Plata on one very dark
night, the sea presented a wonderful and most beautiful
spectacle. There was a fresh breeze, and every part of the
surface, which during the day is seen as foam, now glowed
with a pale light. The vessel drove before her bows two
billows of liquid phosphorus, and in her wake she was followed
by a milky train. As far as the eye reached, the crest
of every wave was bright, and the sky above the horizon,
from the reflected glare of these livid flames, was not so
utterly obscure as over the vault of the heavens.
As we proceed further southward the sea is seldom
phosphorescent; and off Cape Horn I do not recollect more than
once having seen it so, and then it was far from being
brilliant. This circumstance probably has a close connection
with the scarcity of organic beings in that part of the ocean.
After the elaborate paper, [8] by Ehrenberg, on the
phosphorescence of the sea, it is almost superfluous on my part
to make any observations on the subject. I may however
add, that the same torn and irregular particles of gelatinous
matter, described by Ehrenberg, seem in the southern as
well as in the northern hemisphere, to be the common cause
of this phenomenon. The particles were so minute as easily
to pass through fine gauze; yet many were distinctly visible
by the naked eye. The water when placed in a tumbler and
agitated, gave out sparks, but a small portion in a watch-
glass scarcely ever was luminous. Ehrenberg states that
these particles all retain a certain degree of irritability. My
observations, some of which were made directly after taking
up the water, gave a different result. I may also mention,
that having used the net during one night, I allowed it to
become partially dry, and having occasion twelve hours
afterwards to employ it again, I found the whole surface
sparkled as brightly as when first taken out of the water.
It does not appear probable in this case, that the particles
could have remained so long alive.
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