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at all) more than before. If described without reference
to its parentage, it would still be considered an Entomos-
tracous Crustacean, or Water-flea, but removed to another
tribe. It represents, in fact, a Cypris; 1 the body with
its fringed limbs being now included within two convex
valves, like those of a mussel or other bivalve shell, either
united by a hinge along the back, or rather soldered to-
gether there, so as only to allow a slight opening and
closing by the elasticity of their substance. The fore part
of the head is now greatly enlarged, as are also the an-
tennae, which project from the shell. The single eye is
separated into two, which are large and attached to the
outer arms of two bent processes which are placed within
the body, in the form of the letters UU- The legs are in-
creased by the addition of two pairs, and these are doubly
bent in a zig-zag form, and can be protruded from between
the valves.

It is a highly curious fact that the infant Barnacle has
thus passed through two distinct types of animal life, the
Cyclops and the Cypris. These are not one type in differ-
ent stages, as might be reasonably presumed. The young
of Daphnia and of Cyclops are so much alike that it would
be natural to presume the young of Cypris to be of the

1 See figure on page 210.



BARNACLES 231

same form; in which case we should have in the young
Barnacle merely the first and second stages of Cypris.
But it is not so. Cypris does not pass through the Cyclops
form at all; for, according to J urine, the young when
hatched have the appearance of the perfect animal, though
varying a little in the shape of their shells.

It is in this second form, which may be considered the
pupa of the Barnacle, that the animal quits its free roving
life, and becomes a fixture for the remainder of its days.
And this is a most wonderful process; so wonderful, that
it would be utterly incredible, but that the researches of
Mr. Darwin have proved it incontestably to be the means
by which the wisdom of God has ordained that the little
Water- flea should be transformed into a stony Acora
Barnacle.

Having selected a suitable place for fixing its resi-
dence such as those massive rocks which sustain the im-
petuous billows on our sea-worn coasts the great project-
ing antennae manifest a new and unprecedented function.
Glands situated at their base secrete a tenacious glue,
which, being poured out in great profusion, cements the
whole front of the head to the rock, including and con-
cealing the antennae themselves. The cement rapidly sets
under water, and the animal is henceforth immovable.

It now moults its skin once more. Another great
change takes place; the bivalve shell is thrown off, as
are also the eyes with their bent supports, and it is seen
to be a true Barnacle, though as yet of minute dimen-
sions, and with its valves in a very rudimentary condi-
tion. It is now the representative of a third type among
the Crustacean forms, for it is in effect a Stomapod; such
as the Opossum Shrimp (My sis), for example, with the



232 EVENINGS AT THE MICROSCOPE

shield composed of several pieces, stony in texture, on
account of the great development of their calcareous ele-
ment, and so modified in form as to make a low cone, the
legs (become the cirri, or what I have above called the
" fingers 7 ') made to perform their movements backward
instead of forward, and the whole abdomen reduced to
an almost invisible point.

Marvellous indeed are these facts. If such changes as
these, or anything approaching to them, took place in the
history of some familiar domestic animal if the horse, for
instance, was invariably born under the form of a fish,
passed through several modifications of this form, imitat-
ing the shape of the perch, then the pike, then the eel,
by successive castings of its skin; then by another shift
appeared as a bird, and then, gluing itself by its fore-
head to some stone, with its feet in the air, threw off its
covering once more; and became a foal, which then grad-
ually grew into a horse or if some veracious traveller,
some Livingstone or Barth, were to tell us that such proc-
esses were the invariable conditions under which some
beast of burden largely used in the centre of Africa
passed should we not think them very wonderful? Yet
they would not be a whit more wonderful in this sup-
posed case than in the case of the Barnacle, in whose his-
tory they are constantly exhibited in millions of individ-
uals, and have been for ages even in creatures so common
that we cannot take a walk beneath our sea-cliffs, without
treading on them by hundreds!



SPIDERS AND MITES 233



CHAPTER XIII

SPIDERS AND MITES

SPIDERS, I am sure, are not favorites with you. With
the exception of the poor prisoner in the Bastile,
who had succeeded in taming a Spider the only
creature besides himself that inhabited his dungeon I do
not think I have ever heard of any one who loved or
admired Spiders, morally. Yet, physically, we may find
much to admire in them, as not a few naturalists have
done before us; there are men who have devoted their
lives to the study of this unamiable race, and who have
discovered in them the same wondrous skill, and the same
perfect adaptation of organ to function, of structure to
habit, that mark all God's works, whether we think them
pretty or ugly, amiable or repulsive.

I am going to show you some of these pieces of mech-
anism. Remember that the whole tribe is sent into the
world to perform one business they are commissioned to
keep down what would otherwise be a " plague of flies."
They are fly-butchers by profession; and just as our beef
and mutton butchers have their slaughter-house, their
steel, their knives, their pole-axe, their hooks, so are
these little slaughterers furnished with nets and traps,
with caves, with fangs, and hooks, and poison-bags, ready
for their constant work. They have, in fact, nothing elsa
to do: their whole lives are spent in slaughtering with



234 EVENINGS AT THE MICROSCOPE

the exception of rearing fresh, generations of slaughterers
and I suppose they think, and are intended to think,
of nothing else.

I was one day in an omnibus, in the corner of which
sat a butcher. Presently a man got in, whose blue ging-
ham coat indicated the same trade. He seated himself op-
posite the other, and the two were soon in conversation.
"Do you know Jackson?" says A. "No," says B; "where
does he slaughter?" The reply gave me a new idea; he
evidently considered that "slaughtering" was the only oc-
cupation worthy of a man, and therefore the only one
worthy of man's thought. Spiders are just the same. If
an Epeira met a Clubiona, probably the first interchange
of civilities would be something like "Where do you
slaughter?"

"No one," says Professor Eymer Jones, "who looks at
the armature of a Spider's jaws can mistake the intention
with which this terrible apparatus was planned. 'Murder'
is engraved legibly on every piece that enters into its com-
position." But surely the Professor is rather severe. 1
do not think this paragraph was written on an autumn
morning, when the flies had driven him out of bed prema-
turely early, by incessantly alighting on his nose; nor on
coming home from a summer evening's walk through the
marsh, when clouds of singing and stinging gnats had been
the only objects of cognizance to sight, hearing, and feel-
ing. If so, he would have been ready to pronounce "kill-
Ing no murder, ' ' and have blessed the slaughtering Spiders
as pursuing a most praiseworthy and useful occupation.
Circumstances change opinions.

"We will not then touch the moral question; but just
look at this apparatus from the head of one of our com-



SPIDERS AND MITES 235

mon Spiders (Clubiona atrox), a long-legged and swift spe-
cies, that builds a compact cloth-like web in our outhouses,
with a gallery open at each end for retreat in danger. The
specimen is a part of the slough or cast skin, which you
may always find in the neighborhood of such a web; and
it is particularly suitable for examination, because it is
sloughed in the most perfect condition; every part, the
fangs, the palps, the legs with all their joints, the corneas
of the eyes, the entire skin with every hair all are here,
and all in situ, with a cleanness and translucency which it
would require much skill in dissection to obtain, if we
captured a living Spider for our purpose.

There are in front of the head two stout brown organs,
which are the representatives of the antennae in insects;
though very much modified both in form and function.
They are here the effective weapons of attack. Each con-
sists of two joints: the basal one, which forms the most
conspicuous portion of the organ, and the terminal one,
which is the fang. The former is a thick hollow case,
somewhat cylindrical, but flattened sidewise, formed of
stiff chitine, covered with minute transverse ridges on its
whole surface, like the marks left on the sand by the rip-
pling wavelets, and studded with stout coarse black hair.
Its extremity is cut off obliquely, and forms a furrow, the
edges of which are beset with polished conical points re-
sembling teeth.

To the upper end of this furrowed case is fixed by a
hinge-joint the fang, which is a curved claw-like organ,
formed of hard chitine, and consisting of two parts, a
swollen oval base, which is highly polished, and a more
slender tip, the surface of which has a silky lustre, from
being covered with very fine and close-set longitudinal



236 EVENINGS AT THE MICROSCOPE

grooves. This whole organ falls into the furrow of the
basal joint, when not in use, exactly as the blade of a
clasp-knife shuts into the haft; but when the animal is
-excited, either to defend itself or to attack its prey, the
fang becomes stiffly erected.

By turning the object on its axis, and examining the
extreme tip of the fang, we see that it is not brought to a
fine point, but that it has the appearance of having been
cut off slantwise just at the tip; and that it is tubular.
Now this is a provision for the speedy infliction of death
upon the victim; for both the fang and the thick basal
joint are permeated by a slender membranous tube, which
is the poison duct, and which terminates at the open ex-
tremity of the former, while at the other end it commu-
nicates with a lengthened oval sac where the venom is
secreted. This of course we do not see here, for it is not

sloughed with the exuviae, but
retained in the interior of the
body; but in life it is a sac,
L extending into the cephalo-
thorax as that part of the
body which carries the legs is
PANG OF SPIDEB. called and covered with spi-

ral folds produced by the arrangement of the fibres of its
contractile tissue.

When the Spider attacks a fly, it plunges into its
victim the two fangs, the action of which is downward,
and not from right to left, like that of the jaws of Insects.
At the same instant a drop of poison is secreted in each
gland, which, oozing through the duct, escapes from the
perforated end of the fang into the wound, and rapidly
produces death. The fangs are then clasped down, carry-




SPIDERS AND MITES 237

ing the prey, which they powerfully press against the
toothed edges of the stout basal piece, by which means
the nutritive fluids of the prey are pressed out, and taken
into the mouth, when the dried and empty skin is re-
jected. The poison is of an acid nature, as experiments
performed with irritated spiders prove ; litmus-paper pierced
by them becoming red as far around the perforations as
the emitted fluid spreads.

In the slough, the upper surface of the cephalo-thorax
is always detached as a thin plate, convex outwardly, con-
cave inwardly. As it is upon the front portion of this
division of the body that the eyes are situate, the slough
displays these with great clearness and beauty beneath the
microscope. Here you may see them. The whole slough
from its thinness is semi -pellucid, but the eyes transmit
the light with brilliance, not, however, as if they were
simple round holes, because you can discern very mani-
festly a hemispherical glassy coat, by which it is refracted.

It is, however, when we examine the forehead of a liv-
ing or recently killed spider that we see the eyes to advan-
tage. In this example of the same species (Clubiona atrox),
you see them, like polished globes of diamond, sunk into
the solid skin of the head. Their form is unimpeachably
perfect, and the reflection of light from their surface most
brilliant.

The arrangement of these lustrous eyes is worthy of at-
tention. They are generally eight in number in Spiders,
but their relative position varies so much as to afford good
characters by which naturalists have grouped them in gen-
era. In the Clubiona which we have been examining, they
are placed in two nearly straight transverse rows on the
forehead; but as this surface is convex, it follows that the



238 EVENINGS AT THE MICROSCOPE

axis of every eye points in a different direction from that
of its fellows. In Epeira, on the other hand represented
by our great Garden Spider so commonly seen in the cen-
tre of its perpendicular web, on shrubs and in corners of
our gardens the four middle eyes form a square, and the
two lateral ones on each side are placed in contact with
each other.

It is interesting to remark that their arrangement is
not arbitrary, but is ancillary to the varying instincts and
wants of the different kinds. On this subject I will quote




EYES OF SPIDER



to you what Professor Owen says: ' l The position of the
four median ones is the most constant; they generally in-
dicate a square or trapezium, and may be compared with
the median ocelli in hexapod insects. The two, or the two
pairs of lateral ocelli, may be compared with the compound
eyes of insects; the anterior of these has usually a down-
ward aspect, while the posterior looks backward; the va-
riety in the arrangement of the ocelli of Spiders always
bears a constant relation to the general conformation and
habits of the species. Dujes has observed that those Spi-
ders which hide in tubes or lurk in obscure retreats, either



SPIDERS AND MITES 239

underground or in the holes or fissures of walls or rocks,
from which they only emerge to seize a passing prey, have
their eyes aggregated in a close group in the middle of the
forehead, as in the Bird-spider, the Clotho, etc. The Spi-
ders which inhabit short tubes, terminated by a large web
exposed to the open air, have the eyes separated, and more
spread upon the front of the cephalo- thorax. Those Spi-
ders which rest in the centre of a free web, and along
which they frequently traverse, have the eyes supported
on slight prominences which permit a greater divergence
of their axes; this structure is well marked in the genus
Thomisa, the species of which lie in ambuscade in flowers.
Lastly, the spiders called Errantes, or wanderers, have
their eyes still more scattered, the lateral ones being
placed at the margins of the cephalo-thorax. " 1

The shining hemisphere (or nearly a sphere) is in each
case covered with a thick cornea, a continuation of the
skin, perfectly transparent, and throwing off its outer coats
successively in the process of moulting, like that of the
rest of the body. The centre of its inner surface is deeply
excavated for the reception of a crystalline lens, which is
globular in form, and which rests behind on the front sur-
face of a hemispherical vitreous body, without sinking into
it. The space between this body and the side of the lens
forms a ring-like channel which is filled with an aqueous
humor, and into this projects a circular process of the
thick pigment-coat, which corresponds to the choroid, thus
defining the pupil of the eye, and , at the same time con-
fining the lens to its proper situation. The margin of this
pigment-ring may be considered as an iris, and is of vari-

1 "Comp. Anat." (Ed. 2), p. 451.



240 EVENINGS AT THE MICROSCOPE

ous colors, as red, green, or brown in those species which
are active by daylight, while it is black at the back of the
eye. The nocturnal species have no dark pigments, but
are furnished with a curtain (tapetum), which reflects a
brilliant metallic lustre, and makes the eyes of these Spi-
ders glare in the twilight, like those of cats.

It will be interesting to compare with this range of
eyes the same organs in a kindred animal, the common
Harvestman (Phalangium cornutum). Here in the centre
of the cephalo- thorax rises a short pillar, which is crowned
with two rows of conical points, with polished black tips.
On each side of the pillar is a large black eye, hemispher-
ical in form, and brilliantly glossy, exactly resembling,
indeed, those which we have just examined. There are,
however, only this single pair which thus look out later-
ally, exactly like the eyes of Birds. There is, indeed, a
speck on each side of the thorax, considerably removed
from the eye-pillar, just above the origin of the first pair
of legs, which has been mistaken for an eye; but it is
truly a spiracle, or breathing hole.

There are many other points of interest about this Har-
vestman, such as the conical spines which stud the head,
body, and limbs; the multitude of small bead-like joints
into which the foot (tarsus) is divided; and in particular
the hammer-like form of the modified antenna, which bend
abruptly downward, and have pincer-tips. These are highly
curious, and you may examine them at your leisure; but
for the present we will return to our Spiders.

Ever since those mythic times when Arachne con-
tended with Minerva for supremacy in needle-work, and
was changed, for her pains, into a spider, our little spin-
ners have been famous (Spider = Grer. Spinne) for their



SPIDERS AND MITES

matchless achievements in thread. And still their indus-
trious art is plied everywhere around us in our chambers,
in our windows, in our cellars, in our walls, in our gar-
dens, in waste and desert places, and even under water.
But you shall hear what Professor Owen says on the de-
gree and mode in which Spiders exercise their singular
secreting faculty, which " varies considerably in the differ-
ent species. Some, as the Clubionce, line with silk a con-
ical or cylindrical retreat, formed, perhaps, of a coiled-up
leaf, and having an outlet at both extremities, from one of
which may issue threads to entrap their prey. Others, as
the Segestrice, fabricate a silken burrow of five or six inches
in length, in the cleft of an old wall. The Mygale cemen-
taria lines a subterraneous burrow with the same sub-
stance, and manufactures a close-fitting trap-door of ce-
mented earth, lined with silk, and so attached to the entry
of the burrow as to fall down and cover it by its own
weight, and which the inmate can keep close shut by
means of strong attached threads.

"The arrangement of Spiders by M. Walckenaer into
families, characterized by their habits, places the principal
varieties of their webs in a very concise point of view.

"The Cur sores, Saltatores, and Laterigradce, make no
webs: the first catch their prey by swift pursuit; the sec-
ond spring upon their prey by insidious and agile leaps;
the third run, crab-like, sidewise or backward, and occa-
sionally throw out adhesive threads to entrap their prey.
The Latebricolce hide in burrows in fissures, which they line
with a web. The Tubicolce enclose themselves in a silken
tube, strengthened externally by leaves or other foreign
substances. The Niditelce weave a nest whence issue threads

to entrap their prey. The Filitelce are remarkable for the

-SCIENCE 11



242 EVENINGS AT THE MICROSCOPE

iong threads of silk which they spread about in the places
where they prowl in quest of prey. The Lapitelce, spin
great webs of a close texture, like hammocks, and wait for
the insects that may be entangled therein. The Orbitelce
spread abroad webs of a regular and open texture, either
circular or spiral, and remain in the middle, or on one
side, in readiness to spring upon an entangled insect. The
Retitelce spin webs of an open mesh-work and of an irregu-
lar form, and remain in the middle or on one side, to seize
their prey. Lastly, the Aquitelce spread their silken fila-
ments under water, to entrap aquatic insects.

"The silken secretion of Spiders is not applied only to
the formation of a warm and comfortable dwelling for them-
selves, or of a trap for their prey; it is often employed to
master the struggles of a resisting insect, which is bound
round by an extemporary filament, spun for the occasion,
as by a strong cord. It forms the aeronautic filament of
the young migratory brood. It serves to attach the moult-
ing Hydrachna to an aquatic plant by the anterior part of
the body, when it struggles to withdraw itself from its ex-
uvium. Lastly, a softer and more silken kind of web is
prepared for the purpose of receiving the eggs, and to
serve as a nest for the young." '

The silk with which these various fabrics are con-
structed is a thick, viscous, transparent liquid, much like
a solution of gum arabic, which hardens quickly on expos-
ure to the air, but can meanwhile be drawn out into thread.
So far, it agrees with the silk of the silkworm and other
caterpillars; but the apparatus by which it is secreted, and
that by which it is spun, are both far more complex and

1 "Comp. Anat." (Ed. 2), p. 458.



SPIDERS AND MITES __24S

elaborate than those of the latter. Generally speaking,
there are three pairs of spinnerets, or external organs,
through which the threads are produced, but in some few
cases there are only two pairs, and in others, as the Gar-
den Spiders (Epeira), the hindmost pair seem to be united
into a single spinneret. These are always situated at the
hinder extremity of the body, and I will show them to you
presently. First, however, I will describe the internal ap-
paratus the source of the threads.

The glands which secrete the gummy fluid are placed in
the midst of the abdominal viscera, and in some instances
as in the female of Epeira fasciata, a species which
makes a remarkably large web they occupy about a quar-
ter of the whole bulk of the abdomen. About five differ-
ent kinds of these glands may be distinguished, though
they are not all present in every species. The Epeiroe,
however, present them all.

In this genus there are: 1. Small, pear-shaped bags,
associated in groups of hundreds, and leading off by short
tubes, which are interlaced in a screw-like manner, and
open in all of the spinnerets. 2. Six long twisted tubes,
which gradually enlarge into as many pouches, and then
are each protracted into a very long duct, which forms a
double loop. 3. Three pairs of glandular tubes, similar to
the preceding, but which open externally through short
ducts. 4. Two groups of much branched sacs, whose long
ducts run to the upper pair of spinnerets. 5. Two slightly
branched blind-tubes, which terminate by two short ducts
in the middle pair of spinnerets.

It is not very easy to examine the spinnerets with a
microscope, so as to make out their structure. If we con-
fine the Spider in a glass cell, it is so restless that the



244: EVENINGS AT THE MICROSCOPE

least shock or change of position will cause it to move to
and fro; and, besides, when it does become quiescent, the
spinnerets are closed in toward each other, so that we
cannot see their extremities. By selecting a specimen,
however, recently killed, such as this Clubiona, we may
discern sufficient to enable us to comprehend their con-
struction.

Looking, then, at the abdomen from beneath, we see
the three pairs of spinnerets clustered together close to the
extremity. The pair most forward are shaped somewhat
like barrels, whose free ends bend over toward each other.
They are covered with stiff black hairs, and just within
the margin of what may be called the head of the barrel
(for it is cut off horizontally, with a sharp rim), there is
a circle of very close-set, stiff, whitish bristles, which arch
inward. The whole flat surface of the "head," within this
circle of bristles, is beset with very minute horny tubes,
standing erect, which are the outlets of the silk- ducts that
belong to this pair.

Behind this first pair are seen the middle pair, almost
concealed, however, from their shortness and smallness,
and from the approximation of the first and third pairs.
We can discern that they are more teat-like than the pre-
ceding, terminating in a minute wart, which is prolonged
into a horny tube. The whole teat is set with similar



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