glaucus-or the wonders of the shore(格劳高斯)-第42章
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the group。 Another is the higher 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withdrawn； they are gathered up in a bundle； like the stays of an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。
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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。
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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
