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BRANCHIOPODA
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BRANCHIOPODA .—In this See also:order, exclusion of the Phyllocarida will leave three suborders of very unequal extent, the Phyllopoda, Cladocera, Branchiura. The constituents of the last have often been classed as Copepoda, and among the Branchiopods must be regarded as aberrant, since the "branchial tail " implied in the name has no feet, and the actual feet are by no means obviously branchial. Phyllopoda.—This " See also:leaf-footed " suborder has the appendages which follow the second maxillae variable in number, but all foliaceous and branchial, The development begins with a See also:free nauplius See also:stage. In the outward See also:appearance of the adults there is See also:great want of uniformity, one set having their limbs sheltered by no See also:carapace, another having a broad See also:shield over most of them, and a third having a bivalved See also:shell-See also:cover within which the whole See also:body can be enclosed. In See also:accord with these See also:differences the sections may be named Gymnophylla, Notophylla, Conchophylla. The See also:equivalent terms applied by Sars are Anostraca, Notostraca, Conchostraca, involving a termination already appropriated to higher divisions of the Crustacean class, for which it ought to be reserv°d. 1. Gymnophylla.—These singular crustaceans have See also:long soft flexible bodies, the eyes stalked and movable, the first antennae small and filiform, the second lamellar in the See also:female, in the male prehensile; this last See also:character gives rise to some very fanciful developments. There are three families, two of which See also:form companies rather severely limited. Thus the Polyartemiidae, which compensate themselves for their stumpy little tails by having nine-teen instead of the normal eleven pairs of branchial feet, consist exclusively of Polyartemia forcipata (See also:Fischer, 1851). This See also:species from the high See also:north of See also:Europe and See also:Asia carries See also:green eggs, and above them a See also:bright See also:pattern in See also:ultramarine (Sars, 1896, 1897). The Thamnocephalidae have likewise but a single species, Thamnocephalus platyurus (Packard, 1877), which justifies its See also:title " bushy-See also:head of the broad tail " by a singularity at each end. Forward from the head extends a long ramified appendage described as the " frontal See also:shrub," backward from the See also:fourth abdominal segment of the male spreads a fin-like expansion which is unique. In the ravines of See also:Kansas, pools supplied by torrential rains give See also:birth to these and many other phyllopods, and in turn " millions of them perish by the drying up of the pools in See also:July " (Packard). The remaining See also:family, the Branchipodidae, includes eight genera. 1n the long See also:familiar Branchipus, Chirocephalus and Streptocephalus the See also:males have frontal appendages, but these are wanting in the " brine-See also:shrimp " Artemia, and the same want See also:helps to distinguish Branchinecta (Verrill, 1869) from the old genus Branchipus. Of Branchiopsyllus (Sars, 1897) the male is not yet known, but in his genera of the same date, the Siberian Artemiopsis and the See also:South See also:African Branchipodopsis (1898), there is no such appendage. Of the last genus the type species B. hodgsoni belongs to Cape See also:Colony, but the specimens described were See also:born and bred and observed in See also:Norway. For the study of See also:freshwater See also:Entomostraca large possibilities are now opened to the naturalist. A See also:parcel of dried mud, coming for example from See also:Palestine or Queens-See also:land, and after an indefinite See also:interval of See also:time put into See also:water in See also:England or elsewhere, may yield him living forms, both new and old, in the most agreeable variety. Some caution should be used against confounding accidentally introduced indigenous species with those reared from the imported eggs. Those, too, who send or bring the See also:foreign See also:soil should exercise a little thought in the choice of it, since dry See also:earth that has never had any Entomostraca near it at See also:home will not become fertile in them by the See also:mere fact of exportation. 2. Notophylla.—In this See also:division the body is partly covered by a broad shield, See also:united in front with the head; the eyes are sessile, the first antennae are small, the second rudimentary or wanting; of the numerous feet, sometimes sixty-three pairs, exceeding the number of segments to which they are attached, the first pair are more or less unlike the See also:rest, and in the female the See also:eleventh have the epipod and exopod (flabellum and sub-apical See also:lobe of Lankester) modified to form an ovisac. Development begins with a .nauplius stage. Males are very rare. The single family Apodidae contains only two genera, Apus and its very near See also:neighbour Lepidurus. Apus australiensis (See also:Spencer and See also: It remains rather obscure, though the type species originally " was discovered in great abundance in a roadside puddle subject to See also:desiccation." Limnadia (See also:Brongniart, 182o) is supposed to consist of species exclusively parthenogenetic. But when asked to believe that males never occur among these See also:amazons, one cannot but remember how hard It is to prove a negative. (b) The Lynceidae, with not more than twelve pairs of feet. This family is limited to the species, widely distributed, of the single genus Lynceus, established by O. F. See also: Sars (1887) having had the opportunity of raising it from dried Australian mud, found that, unlike other phyllopods, but like the Cladocera, the See also:parent keeps its brood within the shell until their full development. Cladocera.—In this suborder the head is more or less distinct, the rest of the body being in See also:general laterally compressed and covered by a bivalved test. The title " branching horns " alludes to the second antennae, which are two-branched except in the See also:females of Holopedium, with each See also:branch setiferous, composed of only two to four See also:joints. The mandibles are without palp. The pairs of feet are four to six. The eye is single, and in addition to the eye there is often an " eye-spot, "Monospilus being unique in having the eye-spot alone and no eye, while Leydigiopsis (Sars, Igor) has an eye with an eye-spot equal to it or larger. The See also:heart has a pair of venous See also:ostia, often blending into one, and an anterior arterial aorta. Respiration is conducted by the general See also:surface, by the branchial lamina (See also:external branch) of the feet, and the vesicular appendage (when See also:present) at the See also:base of this branch. The " See also:abdomen," behind the limbs, is usually very See also:short, occasionally very long. The " postabdomen," marked off by the two postabdominal setae, usually has See also:teeth or spines, and ends in two denticulate or ciliate claws, or it may be rudimentary, as in See also:Polyphemus. Many species have a See also:special glandular See also:organ at the back of the head, which Sida cr"stallina uses for attaching itself to various See also:objects. The Leydigian or nuchal organ is supposed to be auditory and to contain an otolith. The female See also:lays two kinds of eggs—" summer-eggs," which develop without fertilization, and " See also:winter-eggs" or resting eggs, which require to be fertilized. The latter in the Daphniidae are enclosed in a modified part of the See also:mother's shell, called the ephippium from its resemblance to a See also:saddle in shape and position. In other families a less elaborate See also:case has been observed, for which Scourfield has proposed the See also:term protoophippium. In Leydigia he has recently found a structure almost as complex as that of the Daphniidae. In some families the resting eggs See also:escape into the water without special covering. Only the embryos of Leptodora are known to See also:hatch out in the nauplius stage. Penilia (See also:Dana, 1849) is perhaps the only exclusively marine genus. The great See also:majority of the Cladocera belong to fresh water, but their adaptability is large, since Moina rectirostris (0. F. Muller) can equally enjoy a See also:pond at See also:Blackheath, and near See also:Odessa live in water twice as See also:salt as that of the ocean. In point of See also:size a Cladoceran of 5 mm. is spoken of as See also:colossal. Dr Jules See also:Richard in his revision (1895) retains the sections See also:pro-posed by Sars in 1865, Calyptomera and Gymnomera. The former, with the feet for the most part concealed by the carapace, is sub-divided into two tribes, the Ctenopoda, or " See also:comb-feet," in which the six pairs of similar feet, all branchial and nonprehensile, are furnishedwith setae arranged like the teeth of a comb, and the Anomopoda, or variety-feet," in which the front feet differ from the rest by being more or less prehensile, without branchial larninae.
The Ctenopoda comprise two families: (a) the Holopediidae, with a solitary species, Holopedium gibberum (Zaddach), queerly clothed in a large gelatinous involucre, and found in See also:mountain tarns all over Europe, in large lakes of N. See also:America, and also in shallow ponds and See also:waters at See also:sea-level; (b) the Sididae, with no such involucre, but with seven genera, and rather more than twice as many species. Of Diaphanosoma modiglianii Richard says that at different points of See also:Lake Toba in See also:Sumatra millions of specimens were obtained, among which he had not met with a single male.
The Anomopoda are arranged in four families, all but one very extensive. (a) Daphniidae. Of the seven genera, the See also:cosmopolitan Daphnia contains about See also:loo species and varieties, of which See also: In this family Macrothrix (Baird, 1843) is the earliest genus, among the latest being Grimaldina (Richard, 1892) and Jheringula (Sars, 1900). Dried mud and See also:vegetable debris from S. Paulo in Brazil supplied Sars with representatives of all the three in his See also:Norwegian aquaria, in some of which the little Macrothrix elegans " multiplied to such an extraordinary extent as at last to fill up the water with immense shoals of individuals." " The appearance of male specimens was always contemporary with the first ephippial formation in the females." For Streblocerus
pygmaeus, grown under the same conditions, Sars observes: " This 1s perhaps the smallest of the Cladocera known, and is hardly more than visible to the naked eye," the adult female scarcely exceeding 0.25 mm. Yet in the next family Alonella nana (Baird) disputes the See also:palm and claims to be the smallest of all known See also:Arthropoda. (d) Chydoridae. This family, so commonly called Lynceidae, contains a large number of genera, among which one may usually See also:search in vain, and rightly so, for the genus Lynceus. The See also: The Haplopoda like-See also:wise have but a single family, the Leptodoridae, and this has but the single genus Leptodora (Lilljeborg, 1861). Dr Richard (1895, 1896) gives a Cladoceran bibliography of 6o1 references. Branchiura.—This term was introduced by Thorell in 1864 for the Argulidae, a family which had been transferred to the Branchiopoda by Zenker in 1854, though some-times before and since united with the parasitic Copepoda. Though FIG. 1.-Dolops ranarum the animals have an oral See also:siphon, (Stuhlmann). they do not carry ovisacs like the siphonostomous copepods, but See also:glue their eggs in rows to extraneous objects. Their lateral, See also:compound, feebly movable eyes agree with those of the Phyllopoda. The family are described by Claus as 658 " intermittent parasites," because when gorged they leave their hosts, fishes or frogs, and swim about in freedom 'for a considerable See also:period. The long-known Argulus (0. F. Muller) has the second maxillae transformed into suckers, but in Dolops (Audouin, 1837) (fig. 1), the name of which supersedes the more familiar Gyropeltis (See also:Heller, 1857), these effect See also:attachment by ending in strong hooks (See also:Bouvier, 1897). A third genus, Chonopeltis (Thiele, 1900), has suckers, but has lost its first antennae, at least in the female. OsTRACODA.—The body, seldom in any way segmented, is wholly encased in a bivalved shell, the caudal part strongly inflexed, and almost always ending in a furca. The limbs, including antennae and mouth organs, never exceed seven definite pairs. The first antennae never have more than eight joints. The See also:young usually pass through several stages of development after leaving the egg, and this commonly after, even long after, the egg has See also:left the maternal shell. Parthenogenesis is frequent. The four tribes instituted by Sars in 1865 were reduced to two by G. W. Muller in 1894, the Myodocopa, which almost always have a heart, and the Podocopa, which have none. Myodocopa.—These have the furcal branches broad, lamellar, with at least three pairs of strong spines or ungues. Almost always the shell has a rostral sinus. Muller divides the tribe into three families, Cypridinidae, Halocypridae, and the heartless Polycopidae, which constituted the tribe Cladocopa of Sars. 
From the first of these See also:Brady and See also:Norman distinguish the Asteropidae (fig. 3), remarkable for seven pairs of long branchial leaves which See also:fold over the hinder extremity of the animal, and the Sarsiellidae, still somewhat obscure, besides adding the Rutidermatidae, knowledge of which is based on skilful maceration of minute and long-dried specimens. The Halocypridae are destitute of compound lateral eyes, and have the sexual orifice unsymmetrically placed. Podocopa.—In these the furcal branches are linear or rudimentary, the shell is without rostral sinus, and, besides distinguishing characters of the second 2ntennae, they have always a branchial See also:plate well developed on the first maxillae, which is inconstant in the other tribe. There are five families: (a) Cyprididae (? including Cypridopsidae of Brady and Norman). In some of the genera parthenogenetic See also:propagation is carried to such an extent that of the familiar Cypris it is said, " until quite lately males in this genus were unknown; and up to the present time no male has been found in the See also:British Islands " (Brady and Norman, 1896). On the other See also:hand, the ejaculatory duct with its verticillate See also:sac in the male of Cypris and other genera is a feature scarcely less remarkable. (b) Bairdiidae, which have the valves smooth, with the See also:hinge untoothed. (c) Cytheridae (? including Paradoxostomatidae of Brady and Norman), in which the valves are usually sculptured, with toothed hinge. Of this family the members are almost exclusively marine, but Limnicythere is found in fresh water, and Xestoleberis bromeliarum (Fritz Muller) lives in the water that collects among the leaves.of Bromelias, See also:plants allied to the See also:pine-apples. (d) Darwinulidae, including the single species Darwinula stevensoni, Brady and See also:Robertson, described as " perhaps the most characteristic Entomostracan of the East Anglian Fen See also:District." (e) Cytherellidae, which, unlike the Ostracoda in general, have the hinder part of the body segmented, at least ten segments being distinguishable in the female. They have the valves broad at both ends, and were placed by Sars in a See also:separate tribe, called Platycopa. The range in time of the Ostracoda is so extended that, in G. W. Muller's See also:opinion, their separation into the families now living may have already taken See also:place in the See also:Cambrian period. Their range in space, including See also:carriage by birds, may be co-extensive with the See also:distribution of water, but it is not known what height of temperature or how much chemical See also:adulteration of the water they can sustain, how far they can penetrate underground, nor what are the limits of their activity between the See also:floor and the surface of aquatic expanses, fresh or saline. In individual size they have never been important, and of living forms the largest is one of See also:recent discovery, Crossophorus See also:africanus, a Cypridinid about three-fifths of an See also:inch (15.5 mm.) long; but a length of one or two millimetres is more See also:common, and it may descend to the seventy-fifth of an inch. By multitude they have been, and still are, extremely important. Though the exterior is more See also:uniform than in most See also:groups of See also:Crustacea, the bivalved shell or carapace may be strongly calcified and diversely sculptured (fig. 2), or membranaceous and polished, hairy or smooth, See also:oval or See also:round or See also:bean-shaped, or of some less See also:simple pattern; the valves may See also:fit neatly, or one overlap the other, their hinge may have teeth or be edentulous, and their front partmay be excavated for the protrusion of the antennae or have no such " rostral sinus." By various modifications of their valves and appendages the creatures have become adapted for swimming, creeping, burrowing, or climbing, some of them combining two or more of these activities, for which their structure seems at the first glance little adapted. Considering the imprisonment of the ostracod body within the valves, it is more surprising that the Asteropidae and Cypridinidae should have a pair of compound and sometimes large eyes, in addition to the median organ at the base of the " frontal tentacle," than that other members of the See also:group should be limited to that median organ of sight, or have no eyes at all. The median eye when present FIG. 2.—Cy thereis ornat¢ G. W. may have or not have a Willer). and its three pigment- One eye-space is shown cups may be See also:close together or above on the left. wide apart and the See also:middle one rudimentary. As might be expected, in thickened and highly embossed valves thin spaces occur over the visual organ. The frontal organ varies in form and apparently in See also:function, and is sometimes absent. The first antennae, according to the family, may assist in walking, swimming, burrowing, climbing, grasping, and besides they carry sensory setae, and sometimes they have suckers on their setae (see Brady and Norman on Cypridin¢ norvegica). The second antennae are usually the See also:chief motor-organs for swimming, walking and climbing. The mandibles are normally five-jointed, with remnants of an See also:outer branch on the second See also:joint, the biting edge varying from strong development to evanescence, the terminal joints or " palp " giving the organ a See also:leg-like appearance and function, which disappears in suctorial genera such as Paracytherois. The variable first maxillae are seldom pediform, their function being concerned chiefly with See also:nutrition, sensation and respiration. The variability in form and function of the second maxillae is sufficiently shown by the fact that G. W. Muller, our leading authority, adopts the confusing See also:plan of calling them second maxillae in the Cypridinidae (including Asteropidae), maxillipeds in the Halocypridae and Cyprididae, and first legs in the Bairdiidae, Cytheridae, Polycopidae and Cytherellidae, so that in his See also:fine monograph he uses the term first leg in two quite different senses. The first legs, meaning thereby the See also:sixth pair of appendages, are generally pediform and See also:locomotive, but sometimes unjointed, acting as a See also:kind of brushes to cleanse the furca, while in the Polycopidae they are entirely wanting. The second legs are sometimes wanting, sometimes pediform and locomotive, some-times strangely metamorphosed into the " vermiform organ," generally long, many-jointed, and distally armed with retroverted spines, its function being that of an extremely See also:mobile cleansing See also:foot, which can insert itself among the eggs in the brood-space, between the branchial leaves of Asterope (fig. 3), and even range over the external surface of the valves. The " See also:brush-formed " organs of the Podocopa are medially placed, and, in spite of their some-times forward situation, Muller believes among other possibilities that they and the penis in the Cypridinidae may be alike remnants of a third pair of legs, not homologous with the penis of other Ostracoda FIG. 3.—Asterope arthuri. (Podocopa included). The furca is. Left See also:valve removed. as a See also:rule, a powerful motor-organ, m, End of adductor muscle. and has its laminae edged with strong OC, Eye. teeth (ungues) or setae or both. The Al, Second antenna. young, though born with valves, MX. 1, First maxilla. have at first a nauplian body, and MX. 2, Second maxilla. pass through various stages to p, 1, First foot. maturity. V.O, Vermiform organ. Brady and Norman, in their Mono- BR, Seven branchial leaves. graph of the Ostracoda of the North F, Projecting ungues of the See also:Atlantic and North-Western Europe {See also:urea. (1889), give a bibliography of 125 titles, and in the second part (1896) they give 55 more. The lists are not meant to be exhaustive, any more than G. W. Muller's literature See also:list of 125 titles in 1894. They do not refer to See also:Latreille, 18o2, with whom the term Ostracoda originates. COPEPonA.—The body is not encased in a bivalved shell; its articulated segments are at most eleven, those behind the genital segment being without trace of limbs, but the last almost always carrying a furca. Sexes separate, fertilization by spermatophores. Ova in single or See also:double or rarely several F packets, attached as ovisacs or egg-strings to the genital openings, or enclosed in a dorsal marsupium, or deposited singly or occasion-ally in bundles. The youngest larvae are typical nauplii. The next, the copepodid or cyclopid, stage is characterized by a cylindrical segmented body, with fore- and See also:hind-body distinct, and by having at most six cephalic limbs and two pairs of swimming feet. The order thus defined (see Giesbrecht and Schmeil, Das Tierreich, 1888), with far over a thousand species (See also:Hansen, 1900), embraces forms of extreme diversity, although, when species are known in all their phases and both sexes, they constantly tend to prove that there are no sharply dividing lines between the free-living, the semi-parasitic, and those which in adult See also:life are wholly parasitic and then sometimes grotesquely unlike the normal See also:standard. Giesbrecht and Hansen have shown that the mouth-organs consist of mandibles, first and second maxillae and maxillipeds; and Claus himself relinquished his long-maintained See also:hypothesis that the last two pairs were the separated exopods and endopods of a single pair of append-ages. Thorell's See also:classification (1859) of Gnathostoma, Poecilostoma, Siphonostoma, based on the mouth-organs, was long followed, though almost at the outset shown by Claus to depend on the erroneous supposition that the Poecilostoma were devoid of mandibles. Brady added a new See also:section, Choniostomata, in 1894, and another, Leptostomata, in 19oo, each for a single species. Canu in 1892 proposed two groups, Monoporodelphya and Diporodelphya, the copulatory openings of the female being paired in the latter, unpaired in the former. It may be questioned whether this distinction, however important in itself, would See also:lead to a satisfactory grouping of families. In the same See also:year Giesbrecht proposed his division of the order into Gymnoplea and Podoplea. In appearance an See also:ordinary Copepod is divided into fore- and hind-body, of its eleven segments the composite first being the head, the next five constituting the See also:thorax, and the last five the abdomen. The coalescence of segments, though frequent, does not after a little experience materially confuse the counting. But there is this peculiarity, that the middle segment is some-times continuous with the broader fore-body, sometimes with the narrower hind-body. In the former case the hind-body, consisting only of the abdomen, forms a pleon or tail-part devoid of feet, and the species so constructed are Gymnoplea, those of the naked or footless pleon. In the latter case the middle segment almost always carries with it to the hind-body a pair of rudimentary limbs, whence the term Podoplea, meaning species that have a pleon with feet. It may be objected that hereby the term pleon is used in two different senses, first applying to the abdomen alone and then to the abdomen plus the last thoracic segment. Even this verbal flaw would be obviated if Giesbrecht could prove his tentative hypothesis, that the Gymnoplea may have lost a pre-genital segment of the abdomen, and the Podoplea may have lost the last segment of the thorax. The classification is worked out as follows: I. Gymnoplea.—First segment of hind-body footless, bearing the orifices of the genital organs (in the male unsymmetrically placed); last foot of the fore-body in the male a copulatory organ; neither, or only one, of the first pair of antennae in the male geniculating; cephalic limbs abundantly articulated and provided with many plumose setae; heart generally present. Animals usually free-living, pelagic (Giesbrecht and Schmeil). This group, with 65 genera and four or five See also:hundred species, is divided by Giesbrecht into tribes: (a) Amphaskandria. In this tribe the males have both antennae of the first pair as sensory organs. There is but one family, the Calanidae, but this is a very large one, with 26 genera and more than loo species. Among them is the cosmopolitan Calanus finmarchicus, the earliest described (by See also:Bishop See also:Gunner in 1770) of all the marine free-swimming Copepoda. Among them also is the See also:peacock Calanid, Calocalanus pavo (Dana), with its highly ornamented antennae and gorgeous tail, the most beautiful species of the whole order (fig. 4). (b) Heterarthrandria. Here the males have one or the other of the first pair of antennae modified into a grasping organ for holding the female. There are four families, the Diaptomidae with 27 genera, the Pontellidae with to, the Pseudocyclopidae and Candaeiidae each with one genus. The first of these families is often called Centropagidae, but, as Sars has pointed out, Diaptomus (Westwood, 1836) is theoldest genus in it. Of 177 species valid in the family Giesbrecht and Schmeil assign 67 to Diaptomus. In regard to one of its species Dr Brady says: " In one instance, at least (Talkin See also:Tarn, See also:Cumberland) I have seen the See also:net come up from a See also:depth of 6 or 8 ft. below the Fie. 4.—Calocalanus pavo (Dana). surface with a dense See also:mass consisting almost entirely of D. gracilis." The length of this net-filling species is about a twentieth of an inch. 2. Podoplea.—The first segment of the hind-body almost always with rudimentary pair of feet; orifices of the genital organs (symmetrically placed in both sexes) in the following segment; neither the last foot of the fore-body nor the rudimentary feet just mentioned acting as a copulatory organ in the male; both or neither of the first pair of antennae in the male geniculating; cephalic limbs less abundantly articulated and with fewer plumose setae or none, but with hooks and clasping setae. Heart almost always wanting. Free-living (rarely pelagic) or parasitic (Giesbrecht and Schmeil). This group is also divided by Giesbrecht into two tribes, Ampharthrandna and Isokerandria. In 1892 he distinguished the former as those in which the first antennae of the male have both members modified for holding the female, and the genital openings of the female have a ventral position, sometimes in close proximity, some-times strongly lateral ; the latter as those in which the first antennae of the male are similar to those of the female, the function of holding her being transferred to the male maxillipeds, while the genital openings of the female are dorsal, though at times strongly lateral. In 1899, with a view to the many modifications exhibited by parasitic and semi-parasitic species, the See also:definitions, stripped of a too hampering precision, took a different form: (a) Ampharthrandria. " Swimming Podoplea with geniculating first antennae in the male See also:sex, and descendants of such; first antennae in female and male almost always differently articulated." The families occupy fresh water as well as the sea. Naturally " descendants " which have lost the characteristic feature of the See also:definition cannot be recognized without some further assistance than the definition supplies. Of the families comprised, the Mormonillidae consist only of Mormonilla (Giesbrecht), and are not mentioned by Giesbrecht in 1899 in the grouping of this section. The Thaumatoessidae include Thaumatoessa (Kroyer), established earlier than its synonym Thaumaleus (Kroyer), or than Monstrilla (Dana, 1849). The species are imperfectly known. The defect of mouth-organs probably does not apply to the period of youth, which some of them spend parasitically in the body-cavity of See also:worms (Giard, 1896). To the C'yclopidae six genera are allotted by Giesbrecht in 1900. Cyclops (0. F. Muller, 1776), though greatly restricted since Muller's time, still has several scores of species abundantly peopling inland waters of every kind and situation, without one that can be relied on as exclusively marine like the species of Oithona (Baird). The .Misophriidae are now limited to Misophria (Boeck). The presence of a heart in this genus helps to make it a See also:link between the Podoplea and Gymnoplea, though in various other respects it approaches the next family. The Harpacticidae owe their name to the genus Arpacticus (Milne-See also:Edwards, 1840). Brady in 188o assigns to this family 33 genera and 81 species. Canu (1892) distinguishes eight sub-families, Longipediinae, Peltidiinae, Tachidiinae, Amymoninae, Herpacticinae, Idyinae, Canthocamptinae (for which Canthocampinae should be read), and Nannopinae, adding Stenheliinae (Brady) without distinctive characters for it. The Ascidicolidae have variable characters, showing a See also:gradual See also:adaptation to parasitic life in Tunicates. Giesbrecht (1900) considers Canu quite right in grouping together in this single family those parasites of ascidians, simple and compound, which had been previously distributed among families with the more or less significant names Notodelphyidae, Doropygidae, Buproridae, Schizoproctidae, Kossmechtridae, Enterocolidae, Enteropsidae. Further, he includes in it his own Enterognathus comatulae, not from an ascidian, but from the intestine of the beautiful See also:starfish Antedon rosaceus. The Asterocheridae, which have a See also:good swimming capacity, except in the case of Cancerilla tubulala (See also:Dalyell), lead a semi-parasitic life on echinoderms, See also:sponges, &c., imbibing their See also:food. Giesbrecht, displacing the older name Ascomyzontidae, assigns to this family 21 genera in five subfamilies, and suggests that the long-known but still puzzling Nicothoe from the gills of the See also:lobster might be placed in an additional subfamily, or be made the representative of a closely related family. The Dichelestiidae, on See also:account of their sometimes many-jointed first antennae, are referred also to this tribe by Giesbrecht. (b) Isokerandria. " Swimming Podoplea without genicullating first antennae in the male sex, and descendants of such: First antennae of male and female almost always articulated alike." To this tribe Giesbrecht assigns the families Clausidiidae, Corycaeidae, Oncaeidae, Lichomolgidae, Ergasilidae, Bomolochidae, Clausiidae, Nereicolidae. Here also must for the time be placed the Caligidae, Philichthyidae (Philichthydae of See also:Vogt, See also:Carus, Claus), Lernaeidae, Chondracanthidae, Sphaeronellidae (better known as Choniostomatidae, from H. J. Hansen's remarkable study of the group), Lernaeopodidae, Herpyllobiidae, Entomolepidae. For the distinguishing marks of all these, the number of their genera and species, their habits and trans-formations and dwellings, the reader must be referred to the writings of specialists. Sars (1901) proposed seven suborders—Calanoida, Harpacticoida, Cyclopoida, Notodelphoida, Monstrilloida, Caligoida, Lernaeoida. Additional information and CommentsThere are no comments yet for this article.
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