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saddle adhering to them the two lobes ielle Entomostracan,
saddle adhering to them, and looking like young beans just sprouting from the earth, and carrying with them the two lobes of the seed from which they sprang.
At fig. C is shown a very pretty little Entomostracan, belonging to a small sub-family called the Sidinæ. In all these beings there are six pairs of feet, the lower antennæ have two branches, and a row of sharp and rather strong filaments springs from the edge of the larger branch. In this genus, one branch of the lower antennæ has three and the other two joints. Though it is occasionally very active, passing through the water with great rapidity, it is mostly dull and stationary, having a curious habit of pressing the back of its head against some object, and there remaining for a considerable period without moving. It derives its specific name of crystalline from its beautifully transparent aspect.
In the Lynceidæ there are two pairs of antennæ, the upper being very short, and the branches of the lower having three joints. They have five pairs of legs, and one eye, with a black spot a front of it. The abdomen is jointed. All the species are rapid swimmers, and their food consists of both vegetable and animal matter.
In the Chydorus, of which one or two British species are known, the body is nearly spherical, the lower antennæ are very short, and the beak is very long, sharp, and curved downwards. The colour is olive in the present species, and has a smooth shining exterior. It may be found in ponds and ditches throughout the year.
The curious globular looking creature seen at fig. D is an example of another family, called the Polyphemidæ, having only four pairs of feet, which are not included in the shield. Their single eye is very large, and has given rise to the name of Polyphemus, which belonged to the one-eyed giant overcome by Ulysses and his companions. The lower antennæ have two branches, one with four joints and the other with three. In the lower part of the carapace there is a large empty space for the accommodation of the eggs and young
An example of the typical genus is given at fig. E, which represents the common POLYPHEMUS of our ditches and ponds. In this creature the abdomen is long and projects from the shell, and in the adult the eye is enormously large, seeming to occupy the whole head. There is a deep notch or groove in the Polyphemus, seeming to separate the body from the head. It appears always to swim upon its back, and uses both the antennæ and legs to drive it through the water.
Fig. F will be described presently.
FOLLOWING the arrangement of Dr. Baird, we now come to another section, termed the Lophyropoda, or Plume-footed Entomostraca. In all these animals the mouth is well supplied with teeth, and the body is enclosed in a cuirass, either covering the head and thorax, or shaped like a bivalve shell, and enclosing the whole animal. There are not more than five pairs of feet, only one eye, the gills are few and attached to the mouth, and there are two pairs of antennæ, one pair being used for locomotion.
In the first order, called Ostracoda, a term derived from a Greek word, signifying a · shell, the cuirass is in two parts, and encloses the animal like a bivalve shell The hind jaws are furnished with gills. In the family of the Cypridæ, the upper pair of antenna are long, have numerous joints and a pencil of long filaments; the lower pair are short, thick, and used as feet. There are two pairs of real feet. The CYPRIS, which is represented at fig. A, belongs to a genus which has many British species, and may be found in almost every pond or ditch. The body is enclosed thoroughly in its valved cuirass, something like a walnut in its shell, the fringed antennæ and legs protruding from between the valves and permitting the creature to move. It is a most elegant little being, the shell being gracefully curved, and the antennæ being fine and transparent as if they were threads of glass. Dr. Baird tells us that the valves are very brittle, and that on their exterior they are washed with a kind of varnish which protects them from the action of the water. Owing to this varnish, these creatures cannot venture even to rise to the
surface; for as soon as the shell is exposed to the air, it becomes quite dry, and so buoyant that no exertion of the Cypris can sink it again.
These tiny animals will often live through a hot summer which dries up the pond in which they reside, and at the first rain will make their appearance again, swimming merrily about as if nothing had happened. As soon as they feel themselves being deserted by the water, they bury themselves deeply in the mud, and even their eggs retain their vitality, though the mud should be baked quite hard. When the Cypris changes its skin, it throws off the whole shell, the internal parts of the body, the beautiful comb-like gills, and the tiny hairs which clothe the bristles of the antennæ.
Two more examples of this pretty genus are given in this illustration, fig. B representing Cypris claváta, and fig. C, Cypris vídua, seen from above, in order to show the two valves of the shell and their line of junction. Seventeen or eighteen British species of Cypris are known.
In the family of Cytheridæ, the upper pair of antennæ have no long filaments.
The members of the typical genus Cythere are mostly marine, and may be found in the little rock-pools at the sea-side, darting about among the branches of sea-weeds and zoophytes that live so plentifully in such situations. Safe in these sheltered spots, they care nothing for wind and waves, and the storm which flings the huge whale on the shore will fail to injure these tiny beings, whose very minuteness is their safety. Three species of Cythere are here given. Cythere minna, fig. D, is remarkable for being the largest British species seen by Dr. Baird. Its valves are white. It was found in deep water off Shetland, and taken in a dredge. Cythere inopinata, fig. E, derives its specific name of inopinata or unexpected, from the fact that the creature was found where no one would have expected its presence, namely, in a small pond in Middlesex. It is a very small species, and always remains at the bottom. Its colour is white, and there is a little orange coloured mark on the upper edge. An oblique view of this species has been chosen, in order to show the curious rounded projections upon the middle of each valve.
The Cythere impressa, fig. G, was found in sand at Torquay. The shell is dull black in colour, and is covered with little punctures impressed upon its surface, whence is derived its specific name.
A closely allied genus is represented at fig. F, and is remarkable for the manner in which the valves are ridged, irregular, covered with tubercles, and having their edges boldly toothed. This species was taken in the Isle of Skye.
In the family of the Cypridinadæ there are two eyes, set as footstalks, and two pairs of feet, one pair being always within the shell. There is only one genus of these creatures, and all the species are marine. The shell is oval, sharply pointed at each end, and the front edge is deeply notched. The pair of feet that are retained within the shell are modified into one organ, which seems to be intended for the purpose of supporting the eggs. At fig. H is seen this curious organ. The present species was procured in seventy fathoms of water, near the Isle of Skye. Some of the exotic species are luminous.
The next order is termed the Copepodæ, or Oar-footed Entomostracans, because the five pairs of feet are mostly used for swimming. The body is divided into several rings, the cuirass covers both the head and thorax, and the mouth is furnished with foot-jaws.
In the family of the Cyclopidæ the head and body are merged together with the first ring of the thorax. There are two pairs of foot-jaws, and the fifth pair of legs are very minute.
The species which is represented at fig. F on the illustration at page 635 is very common in every pond and ditch, and the female may at once be recognised by the little egg-bags which she bears on the sides of the abdomen, like John Gilpin's winebottles at his belt. The colour of this species is exceedingly variable, differing according to the locality where the creature happens to reside. It is mostly white, but some individuals are brown, others greenish, while a few are red. Both salt and fresh water are inhabited by the CYCLOPS, and some of the marine species are so highly luminous, that they add in no slight degree to the phosphorescence of the ocean. At figs. G and I are shown specimens of the young in two stages of their growth.
TURNING again to the engraving on page 637, and referring to fig. I, we find a little creature with a long abdomen, which it is able to turn over its back, something after the fashion of the earwig or the cocktail beetles. In this Canthocamptus the thorax and abdomen are merged into each other, and gradually diminish in size to the extremiir. All the species belonging to this genus have very small and simple foot-jaws. It inhabits ponds and ditches of fresh water. Mr. Tuffen West tells me that in February, 1861, he was examining some of the slime that had gathered upon the roof of the Cramlington Pit, at a vast depth from the surface, and that he found in the slime some of these minute crustaceans quite brisk and lively, whisking their tails up and down smartly, as shown in the figure. These creatures must have been washed down the pit while still unhatched, and have been thus carried down from the open air into the bowels of the earth.
Fig. K represents a creature, which though very small, not more than the sixth or seventh of an inch in length, is of exceeding importance to commerce, as it affords food to the herring, several whales, and other valuable beings. In the seas where this little creature lives, whole tracts are reddened with the multitude of their hosts, which swarm near the surface, and congregate in such vast numbers, that the wind has been known to catch up a whole bank of them, like a wave, and fling it into the vessel, covering the deck and the sailors with their bodies. The codfish feeds largely and luxuriously upon these abundant creatures, needing not to take any pains about them, but swimming lazily through their masses and opening its mouth, into which they pass without the least trouble.
The long antennæ are used as oars, being thrown backward at every stroke until their tips touch each other. This attitude, however, is only assumed while the creature is in haste, as it is often seen to pass gently through the water, with its antennæ at right angles to the body, as shown in the engraving. Dr. Sutherland, in his “ Voyage to Bathin's Bay," writes of these elegant little beings :-“ They are always on the alert to elude and escape from their pursuers. When the water is but slightly agitated, they dive from the
surface, and in a few minutes, when it becomes still, they can be seen ascending slowly, but rarely using the antennæ. I could only obtain specimens by including them in a large quantity of water taken up suddenly, from which they could be separated subsequently by straining through a calico bag. A bucketful (two gallons) of water often produced twenty to thirty individuals, and sometimes twice that number. They never survived a single night, even though kept in their native element in a vessel. From their constant darting from side to side of the vessel, perhaps it is a safe inference that the fear of danger in their new situation may be one of the chief causes of the early extinction of life.”
The colour of this species is light red, and the body is nearly translucent.
Another curious species deserves a word of mention. This is the Notodelphys ascidicola, which is fonnd swimming in the bronchial sac of the ascidia.
In this illustration we have 'examples of a group of Entomostraca which are parasitic upon fish and other inhabitants of the waters. They belong to Dr. Baird's third legion, called the Pæcilopoda, a term derived from two Greek words, signifying various - footed. They are so named because they are partly formed for walking or seizing prey, and partly for swimming and breathing. In the first order, the SIPHONOSTOMA, or tube-mouthed Entomostraca, the mouth is furnished with a tube containing sharp spikelike mandibles. The foot-jaws are well formed. The object of the tube and its sharp mandibles is evidently for the purpose of piercing the skin and sucking the juices of the beings upon which they cling, and the strong foot-jaws enable them to hold so firnily that they cannot be shaken off. The first tribe is called Peltocephala, or bucklerheaded, because the head is shaped something like an ancient buckler; the head is also furnished with plates in front, and small antennæ of two joints. The first family of these creatures is called Argulidæ, and may be known by the circular shaped head shield, and the manner in which the second pair of foot-jaws are modified into a pair of powerful suckers.
A. 'Argulus foliaceus. B. Caligus Afulleri. The FISH-ARGULUS may be seen upon many
C. Nicóthoë ástaci. (Natural size.) of the ordinary river-fishes of England, the stickle
D. Nicothoë ástaci. (Female, magnified.) back being its favourite. I have seen it on the
E. Nicothoë ástaci. (Male, magnified.) roach, and even upon the golden carp. It is not
F. Dichelestium sturiónis. very small, being about the diameter of a small G. Chondracanthus zei. H. Lernæodiscus.
I. Jacculina. sweet pea, and may easily be watched if placed in an aquarium in which any fish are swimming. The little creature at once makes for the fish, darting along with considerable speed, and fixes itself to the side just under the pectoral fins. It does not, however, remain fixed to the fish, but occasionally leaves it, and starts off on little voyages of discovery, always, however, returning at short intervals, as if for the purpose of assuring itself of a meal. It is wonderfully flat, looking very
like the shed seed-vessel of some plant, and the resemblance is increased by its pale green colour.
The female is considerably larger than the male, and may at once be known by the black spot on each side of the abdomen.
The CALIGUS, which is shown at fig. B, is referred to another family.
This creature is mostly found upon the codfish and brill, and clings with great firmness. Mr. Tuffen West tells me that he has examined the Caligus carefully with the microscope, and assured himself that the suckers are present. “They are hemispherical, shallow in front, where their margin thins off to a translucent membrane; and deep behind, where their concavity is bounded by a strong transversely striated membrane. The figure is magnified about two diameters.
Figs. C, D, and E represent a remarkable parasite, adherent to the gills of the lobster. This creature belongs to a different tribe, which may be known by the small and mostly blunt head, and the long and well-jointed antennæ. The family Ergasilidæ have the head rounded, the body oval, the abdomen well developed, and the feet small and branched.
The LOBSTER-LOUSE is sometimes found in considerable numbers fixed to the gills of the lobster, from which the female never moves after she has once taken a firm hold, though the male is more erratic in his habits, and swims about as he chooses. At fig. C it is shown of its natural size among the lobster-gills, which are popularly termed the “lady's fingers." At fig. D is seen a magnified figure of the female, and at E a figure of the male, also enlarged. During her early youth, the female is not much larger than the male, but as soon as she attaches herself to her new home, a pair of strange projections are seen to grow from the side, and by degrees become so large that they seem to constitute the entire creature. Below these projections the egg-sacs are developed.
At fig. F is seen a curious parasite that infests the sturgeon.
The Dichelestium is rather more than half an inch in length and the twelfth of an inch in breadth. This creature insinuates itself deeply into the skin, making its way to the bony arches upon which the gills are supported, but not appearing to touch the membranous gills themselves. Sometimes as many as ten or twelve are taken from a single fish. They can grasp very firmly by means of their forceps, and are able to turn round whenever they please. This curious creature belongs to the order of the Lerneada, in which the mouth is formed for suction, and the limbs scarcely visible. All these beings are parasitic upon fishes, and are often so deeply buried in the tissues that the whole body is concealed and only the egg-bearing tubes suffered to appear. As is the case with many creatures, especially those that occupy a low place in the scale of creation, the young enjoy a wider range than the parent, being able to roam about at will, and not settling down to a motionless existence until they have attained maturity. The figure represents the female Dichelestium.
There seems to be no bound to the wondrous forms which these parasites assume. Fig. G represents the Chondracanthus, so called because its body is covered with cartilaginous spines or tubercles. The name is derived from two Greek words, the former signifying cartilage, and the second a thorn. The broad and flattened egg-tubes are seen below. This strange being is found upon the gills of the John Dory.
At figs. H and I are seen two most extraordinary beings, which were discovered under the abdomen of a lobster. In both these creatures (which certainly seem to belong to the Lerneans), the whole of the head becomes modified into a set of branching fibres, much resembling the roots of a tree. There is no mouth whatever, all nourishment being transmitted through these fibres. They are quite recent discoveries, and after the engraving had been prepared, several of the figures were removed in order to make way for forins s0 novel, so interesting, and so unique.
MORE fish parasites are given in this illustration, many of them possessing the most bizarre and unexpected forms. As our space is rapidly diminishing, these creatures must be very slightly treated.