They

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. 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 found 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 Pocilopoda, 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 firmly 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.

B. Caligus Mülleri.
(Natural size.)
D. Nicóthoë ástaci. (Female, magnified.)
E. Nicóthoë ástaci. (Male, magnified.)
F. Dichelestium sturiónis.
H. Lerncodiscus.

G. Chondracanthus zei.
I. Jacculina.

The FISH-ARGULUS may be seen upon many of the ordinary river-fishes of England, the stickleback being its favourite. I have seen it on the roach, and even upon the golden carp. It is not very small, being about the diameter of a small 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 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 Ergasilida 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 forms so 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 mast be very slightly treated.

PARASITES UPON PARASITES.

641

Fig. A represents the PERCH-SUCKER, and fig. B the male of the same species. The reader will notice the strange formation of the female, and the great dissimilarity between herself and her small mate. Fig. C exhibits an example of a curious genus termed Anchorella, in which the arm-like appendages are very short, and united from the base so as to look like a single organ. At fig. C is seen the female Anchorella uncinata. In this species the body is white, and the short arms end in a rounded knob. This creature is rather more than half an inch in length. At fig. D is shown the male of the same species, which would hardly be recognised as having any connexion with the long bodied creature that has just been described. The length of the male is about the forty-eighth of an inch in length. At fig. E is another species of the same genus, Anchorella rugosa, so called because the body is notched at the side. This creature is about the seventh of an inch in length. All these creatures infest the cod, haddock, and similar fishes.

A wonderful example of a parasitic crustacean in several stages of development is seen at figs. H, I, K. This is the Tracheliastes, with its long egg-bags and strangely developed upper extremity. At fig. I is seen the same creature when very young, and at fig. K it is again shown, though of larger size.

In the next tribe of Entomostraca the head is kept buried in the tissues of the animal to which the parasites cling, and are there held firmly by some horn-like processes that spring from the back part of the head. They are, in fact, living spears, the barbed heads being sunk into their prey. Two curious forms are shown at figs. L and M. The former represents the female of Lamproglena pulchella, and is given in order to show the under surface of the body and the small pairs of feet. These feet show that it belongs to the family of the Penellada. Fig. M represents the Lernentoma asellina. This is also a female.

G

M

A. Acthéres percárum. (Female.)
B. Acthères percárum. (Male)
C. Anchorella uncináta. (Female.)
D. Anchorella uncináta. (Male.)
E. Anchorella rugósa. (Female.)
F. Lernéntoma cornúta. (Female.)
G. Lernéntoma cornuta. (Male.)
H. Tracheliastes polycolpus. (Female.)
I, K. Tracheliastes polycolpus. (Young.)
L. Lamprogléna pulchella. (Female.)
M. Lernéntoma asellina. (Female.)

TURNING to the next engraving, we shall find some more examples of these strange beings. Not the least strange is that which is shown at fig. A, inasmuch as it is parasitical upon a parasite. This is the Chalinius scombri, which is found adhering to a caligus. At fig. A a much magnified drawing is given, showing the long tube and sucker whereby it adheres to its prey, and at fig. B the creature is seen hanging to the lower part of the caligus like a fish at the end of a line.

This is one of the many

instances that prove the truth of that quaint and far-seeing old saying, namely—

Fig. C shows the Cecrops, a creature that is found upon the sunfish, and adheres to the gills. It is not always fixed to this habitation, but floats about by thousands in the Mediterranean, where it is preyed upon by many fishes.

Fig. D shows the female of the SHARK-SUCKER, a species that is found adherent to the eyes of the Arctic shark, and appears to blind it. The sharks to which this unpleasant appendage was attached seemed to be quite destitute of sight, and did not flinch in the least when a blow with a lance was aimed at them. The armlike appendages of this creature are inserted into the corner of the eye for nearly one-fourth of their length. This parasite attains to the length of three inches. Fig. E represents the male of the same species. Fig. F is the male of an allied species found on one of the common dog-fishes known by the name of tope, and described on page 208 of this volume. Fig. G is the female of the same species. At fig. H is seen a strange elongated creature called Penella filosa from its extreme length. This species is found to penetrate into the flesh of the sword-fish, the tunny, and the mole-fish, all of which have been described in this volume. It is said to cause them considerable pain. At fig. I is seen a parasite of even stranger form, but belonging to the same genus. This is Penella sagittata. At fig. K is shown the head of the sprat, having one of these parasites, called the SPRAT-SUCKER, affixed to its eye. Sometimes this creature is tolerably common, many specimens being obtainable at a single fishmonger's shop, while for several years hardly one will be seen. The colour of this parasite is pale sea-green with a slight bluish cast. The eggs are very green. A magnified figure of this creature is seen at fig. L and is given in order to show the barb-like head by which it adheres to the eye of its victim.

At fig. M is shown a strange and seemingly shapeless parasite that is found to affix itself to the carp tribe, and at N a creature of somewhat similar form is notable for being found upon the gills of the codfish. This creature belongs to the typical genus. At

THE PHOXICHILIDIUM.

643

figs. O and P are given two more forms of this genus, which are evidently of a much less perfect type than the preceding species, and, according to the language of naturalists, are said to be degraded forms.

IT is hardly possible to imagine any forms that are so strange, any habits so astonishing as those which are found in the crustaceans figured in this illustration. Although they have been known for some

time, their proper place in the scale of creation has long been a disputed point among systematic naturalists, some considering them to belong to the crustaceans and others to the spiders. As, however, they undergo a true metamorphosis, which is not the case with any spider, they are now admitted to be real, but unique crustacea. Even such naturalists as Siebold and Milne-Edwards differed about them, the former placing them among the spiders and the latter ranking them with the crustacea.

Such strange creatures as these are not easily described, especially when the space that can be granted to them is so limited, for their whole economy is so thoroughly unique that they require a volume rather than a page. They are found upon the British coasts, and their history is briefly as follows.

At figs. B and C of the accompanying illustration are seen two strange-looking creatures with wonderfully small bodies and enormous legs, jointed and arranged in such a manner as almost to preclude the idea of their real character. Indeed, it seems passing strange how the tiny abdomen can absorb sufficient nutriment for the supply of those marvellous limbs.

Their economy is as strange as their form.

Some specimens of a well-known zoophyte (Coryne eximium) are seen growing as they appear while attached to the rocks or sea bed, and upon the branches are shown numerous pear-shaped objects, attached in a manner that reminds the observer of the tropical gourds. On opening these nodules, each is found to contain a specimen of the Phoxichilidium, which, in spite of the long limbs, is packed away in a very complete manner, the limbs being rolled round the body so as to form the creature into a kind of ball. At fig. I one of these beings is shown as it appears when removed from the envelope. The lower part of the engraving

A. Pycnogonum littorale.

B. Phoxichilidium coccinium. (Male.)
C. Phoxichilidium coccinium. (Female.)
D, E, F. Phorichilidium coccinium.
(Young in different stages.)

G. Phoxichilidium coccinium.
(Enclosed in swellings of Coryne eximium.)

H. Phoxichilidium coccinium. (Young nearly complete.)
I. Phoxichilidium coccinium. (Removed from coryne.)
K. Phoxichilidium coccinium. (Just before maturity.)

shows the young Phoxichilidium at different stages of its growth. Sometimes it possesses the rudiments of limbs, with long filamentous appendages; sometimes it throws them off, and contents itself with a pair of stout claws, and then again grows a fresh set of limbs and a pair of small and feeble claws.