按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
organization of the internal parts。 The mouth； surrounded by
tentacles； leads by gullet and gizzard through a channel into a
digesting stomach； from which the rejectable matter passes upwards
through an intestinal canal till it is discharged near the mouth。
The tentacles also differ much from those of true Polypes。 Instead
of being fleshy and contractile； they are rather stiff； resembling
spun glass； set on the sides with vibrating cilia； which by their
motion up one side and down the other of each tentacle； produce a
current which impels their living food into the mouth。 When these
tentacles are withdrawn； they are gathered up in a bundle； like the
stays of an umbrella。 Our Plate I。 contains the following examples
of Polyzoa。
VALKERIA CUSCUTA。 PL。 I。 FIG。 3。
From a group in one of Mr。 Lloyd's vases。 Fig。 3 A is the natural
size of the central group of cells； in a specimen coiled round a
thread…like weed。 Underneath this is the same portion enlarged。
When magnified to this apparent size； the cells could be seen in
different states； some closed； and others with their bodies
protruded。 When magnified to 3 D； we could pleasantly watch the
gradual eversion of the membrane； then the points of the tentacles
slowly appearing； and then； when fully protruded； suddenly
expanding into a bell…shaped circle。 This was their usual
appearance； but sometimes they could be noticed bending inwards； as
in fig。 3 C； as if to imprison some living atom of importance。
Fig。 B represents two tentacles； showing the direction in which the
cilia vibrate。
CRISIA DENTICULATA。 PL。 I。 FIG。 4。
I have only drawn the cells from a prepared specimen。 The polypes
are like those described above。
GEMELLARIA LORICATA。 PL。 I。 FIG。 5。
Here the cells are placed in pairs； back to back。 5 A is a very
small portion on the natural scale。
CELLULARIA CILIATA。 Pl。 I。 FIG。 7
The cells are alternate on the stem； and are curiously armed with
long whip…like cilia or spines。 On the back of some of the cells
is a very strange appendage； the use of which is not with certainty
ascertained。 It is a minute body； slightly resembling a vulture's
head； with a movable lower beak。 The whole head keeps up a nodding
motion； and the movable beak occasionally opens widely； and then
suddenly snaps to with a jerk。 It has been seen to hold an
animalcule between its jaws till the latter has died； but it has no
power to communicate the prey to the polype in its cell or to
swallow and digest it on its own account。 It is certainly not an
independent parasite； as has been supposed； and yet its purpose in
the animal economy is a mystery。 Mr。 Gosse conjectures that its
use may be； by holding animalcules till they die and decay； to
attract by their putrescence crowds of other animalcules； which may
thus be drawn within the influence of the polype's ciliated
tentacles。 Fig。 7 B shows the form of one of these 〃birds' heads；〃
and fig。 7 C； its position on the cell。
FLUSTRA LINEATA。 PL。 I。 FIG。 1。
In Flustrae； the cells are placed side by side on an expanded
membrane。 Fig。 1 represents the general appearance of a species
which at least resembles F。 lineata as figured in Johnston's work。
It is spread upon a Fucus。 Fig。 A is an enlarged view of the
cells。
FLUSTRA FOLIACEA。 PL。 I。 FIG。 2。
We figure a frond or two of the common species； which has cells on
both sides。 It is rarely that the polypes can be seen in a state
of expansion。
SERIALARIA LENDIGERA。 PL。 I。 fig。 10。
NOTAMIA BURSARIA。 PL。 I。 fig。 11。
The 〃tobacco…pipe〃〃 appendages； fig。 11 B； are of unknown use：
they are probably analogous to the birds' heads in the Cellularae。
PLATE V。
CORALS AND SEA ANEMONES。
CARYOPHYLLAEA SMITHII。 PL。 V。 FIG。 2。 PL。 VI。 FIG。 3。
THE connection between Brainstones； Mushroom Corals； and other
Madrepores abounding on Polynesian reefs； and the 〃Sea Anemones；〃
which have lately become so familiar to us all； can be seen by
comparing our comparatively insignificant C。 Smithii with our
commonest species of Actinia and Sagartia。 The former is a
beautiful object when the fleshy part and tentacles are wholly or
partially expanded。 Like Actinia； it has a membranous covering； a
simple sac…like stomach； a central mouth； a disk surrounded by
contractile and adhesive tentacles。 Unlike Actinia； it is fixed to
submarine bodies； to which it is glued in very early life； and
cannot change its place。 Unlike Actinia； its body is supported by
a stony skeleton of calcareous plates arranged edgewise so as to
radiate from the centre。 But as we find some Molluscs furnished
with a shell； and others even of the same character and habits
without one； so we find that in spite of this seemingly important
difference； the animals are very similar in their nature。 Since
the introduction of glass tanks we have opportunities of seeing
anemones crawling up the sides； so as to exhibit their entire basal
disk； and then we may observe lightly coloured lines of a less
transparent substance than the interstices； radiating from the
margin to the centre； some short； others reaching the entire
distance； and arranged in exactly the same manner as the plates of
Caryophyllaea。 These are doubtless flexible walls of compartments
dividing the fleshy parts of the softer animals； and corresponding
with the septa of the coral。 Fig。 2 A represents a section of the
latter； to be compared with the basal disk of Sagartia。
SAGARTIA ANGUICOMA。 PL。 V。 FIG。 3； A； B。
This genus has been separated from Actinia on account of its habit
of throwing out threads when irritated。 Although my specimens
often assumed the form represented in fig。 3； Mr。 Lloyd informs me
that it must have arisen from unhealthiness of condition； its usual
habit being to contract into a more flattened form。 When fully
expanded； its transparent and lengthened tentacles present a
beautiful appearance。 Fig。 3 A； showing a basal disk； is given for
the purpose already described。
BALANOPHYLLAEA REGIA。 PL。 V。 FIG。 1。
Another species of British madrepore； found by Mr。 Gosse at
Ilfracombe； and by Mr。 Kingsley at Lundy Island。 It is smaller
than O。 Smithii； of a very bright colour； and always covers the
upper part of its bony skeleton； in which the plates are
differently arranged from those of the smaller species。 Fig。 1
shows the tentacles expanded in an unusual degree； 1 A； animal
contracted； 1 B； the coral； 1 C； a tentacle enlarged。
PLATE VI。
CORALS AND SEA ANEMONES。
ACTINIA MESEMBRYANTHEMUM。 PL。 VI。 FIG。 1 A。
This common species is more frequently met with than many others；
because it prefers shallow water； and often lives high up among
rocks which are only covered by the sea at very high tide； so that
the creature can； if it will； spend but a short portion of its time
immersed。 When uncovered by the tide； it gathers up its leathery
tunic； and presents the appearance of fig。 1 A。 When under water
it may often be seen expanding its flower…like disk and moving its
feelers in search of food。 These feelers have a certain power of
adhesion； and any not too vigorous animals which they touch are
easily drawn towards the centre and swallowed。 Around the margin
of the tunic are seen peeping out between the tentacles certain
bright blue globules looking very like eyes； but whose purpose is
not exactly ascertained。 Fig。 1 represents the disk only partially
expanded。
BUNODES CRASSICORNIS。 PL。 VI。 FIG。 2。
This genus of Actinioid zoophytes is distinguished from Actinia
proper by the tubercles or warts which stud the outer covering of
the animal。 In B。 gemmacea these warts are arranged symmetrically；
so as to give a peculiarly jewelled appearance to the body。 Being
of a large size； the tentacles of B。 crassicornis exhibit in great
perfection the adhesive powers produced by the nettling threads
which proceed from them。
CARYOPHYLLAEA SMITHII。 PL。 VI。 FIG。 3。
This figure is to show a whiter variety； with the flesh and
tentacles fully expanded
PLATE VIII。
MOLLUSCA。
NASSA RETICULATA。 PL。 VIII。 fig。 2； A； B； C； D； E； F
A VERY active Mollusc； given here chiefly on account of the
opportunity afforded by the birth of young fry in Mr。 Lloyd's
tanks。 The NASSA feeds on small animalcules； for which； in
aquaria； it may be seen routing among the sand and stones；
sometimes burying itself among them so as only to show its caudal
tube moving along between them。 A pair of Nassae in Mr。 Lloyd's
collection； deposited； on the 5th of April； about fifty capsules or
bags of eggs u