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SYSTEMS OF

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Originally appearing in Volume V28, Page 1030 of the 1911 Encyclopedia Britannica.
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SYSTEMS OF CLASSIFICATION Morphography includes the systematic exploration and tabulation of the facts involved in the recognition of all the recent and extinct kinds of animals and their distribution in space and time. (I) The museum-makers of old days and their modern representatives the curators and describers of zoo-logical collections, (2) early explorers and modern naturalist-travellers and writers on zoo-geography, and (3) collectors of fossils and palaeontologists are the chief varieties of zoological workers coming under this head. Gradually since the time of Hunter and Cuvier anatomical study has associated itself with the more superficial morphography until to-day no one considers a study of animal form of any value which does not include internal structure, histology and embryology in its scope. The real dawn of zoology after the legendary period of the middle ages is connected with the name of an Englishman, Edward Edward Wotton, born at Oxford in 1492, who practised wotton. as a physician in London and died in 1555. He published a treatise De differentiis animalium at Paris in 1552. In many respects Wotton was simply an exponent of Aristotle, whose teaching,. with various fanciful additions, constituted the real basis of zoological knowledge throughout the middle ages. It was Wotton's merit that he rejected the legendary and fantastic accretions, and returned to Aristotle and the observation of nature. The most ready means of noting the progress of zoology during the 16th; 17th and 18th centuries is to compare the Aristotle's classificatory conceptions of successive naturalists classif- with those which are to be found in the works of canon. Aristotle himself. Aristotle did not definitely and in tabular form propound a classification of animals, but from a study of his treatises Historia animalium, De generatione animalium, and De partibus animalium the following classification can be arrived at : A. "Evauµa, blood-holding animals (= Vertebrate). I. Zworo'.ouvra iv airrois, viviparous Enaema (=Mammals, including the Whale). 2. "Ops Oss (=Birds). 3. TtrpalroIa aaoba horosouvra, four-footed or legless Enaema which lay eggs (=Reptiles and Amphibia). 4 'IrKsc (=Fishes). X ZVIIi . 35B. "Avalon, bloodless animals ( = Invertebrata). 1. Ma?obaa, soft-bodied Anaema (=Cephalopoda). 2. MaXaKOOrpwca, soft-shelled Anaema (=Crustacea). 3. "Eprsµa, insected Anaema or Insects (=Arthropoda, exclusive of Crustacea). 4. 'OorpaeoIEpoara, shell-bearing Anaema (=Echini, Gastropoda and Lamellibranchiu). Wotton follows Aristotle' in the division of animals into the Enaema and the Anaema, and in fact in the recognition of all the groups above given, adding only one large group wotton's to those recognized by Aristotle under the Anaema, modittcanamely, the group of Zoophyte, in which Wotton !tons. includes the Holothuriae, Star-Fishes, Medusae, Sea-Anemones and Sponges. Wotton divides the viviparous quadrupeds into the many-toed, double-hoofed and single-hoofed. By the introduction of a method of classification which was due to the superficial Pliny—depending, not on structure, but on the medium inhabited by an animal, whether earth, air or water—Wotton is led to associate Fishes and Whales as aquatic animals. But this is only a momentary lapse, for he broadly distinguishes the two kinds. The Swiss professor, Konrad Gesner (1516-1565), is the most voluminous and instructive of these earliest writers on systematic zoology, and was so highly esteemed that his Historia animalium was republished a hundred years after his death. His great work appeared in successive parts—e.g. Vivipara, ovipara, ayes, Pisces, serpentes et scorpio —and contains descriptions and illustrations of a large number of animal forms with reference to the lands inhabited by them. Gesner's work, like that of John Johnstone (b. 1603), who was of Scottish descent and studied at St Andrews, and like that of Ulysses Aldrovandi of Bologna (b. 1522), was essentially a compilation, more or less critical, of all such records, pictures and relations concerning beasts, birds, reptiles, fishes and monsters as could be gathered together by one reading in the great Libraries of Europe, travelling from city to city, and frequenting the company of those who either had themselves passed into distant lands or possessed the letters written and sometimes the specimens brought home by adventurous persons. The exploration of parts of the New World next brought to hand descriptions and specimens of many novel forms of animal life, and in the latter part of the 16th century and the Medical beginning of the r 7th that careful study by " special- anatomists " of the structure and life-history of particular Isis and groups of animals was commenced, which, directed at at first to common and familiar kinds, was gradually extended until it formed a sufficient body of knowledge to serve as an anatomical basis for classification. This minuter study had two origins, one in the researches of the medical anatomists, such as Fabricius (1537-1619), Severinus (1580-1656), Harvey (1578-1657), and Tyson (1649-1708), the other in the careful work of the entomologists and first microscopists, such as Malpighi (1628-1694), Swammerdam (1637-168o), and Hook (1635-1702). The commencement of anatomical investigations deserves notice here as influencing the general accuracy and minuteness with which zoological work was prosecuted, but it was not until a late date that their full influence was brought to bear upon systematic zoology by Georges Cuvier (1769-1832). The most prominent name between that of Gesner and Linnaeus in the history of systematic zoology is that of John Ray (1628-1705). A chief merit of Ray is to have John limited the term " species " and to have assigned to Ran it the significance which it bore till the Darwinian era, whereas previously it was loosely and vaguely applied. He also made 1 If we remember that by " blood " Aristotle understood " red blood," and that he did not know of the existence of colourless blood, his primary division is not a bad one. One can imagine the interest and astonishment with which the great Greek would have been filled had some unduly precocious disciple shown to him the red-blood-system of the marine terrestrial Annelids; the red blood of Flanorbis, of A pus cancriformis, and of the Mediterranean razor shell, Solen legumen. 3. 4. 5. Gearless considerable use of anatomical characters in his definitions of larger groups, and may thus be considered as the father of modern zoology. Associated with Ray in his work, and more especially occupied with the study of the Worms and Mollusca, was Martin Lister (1638–1712), celebrated also as the author of the first geological map. After Ray's death the progress of anatomical knowledge, and of the discovery and illustration of new forms of animal life From from distant lands, continued with increasing vigour. Rayto We note the names of Vallisnieri (1661–1730) and Linnaeus. Alexander Monro (1647–1767) the travellers Tournefort (1656–1708) and Shaw (1692–1751); the collectors Rumphius (1637–1706) and Hans Sloane (166o–17S3); the entomologist Reaumur (1683–1757); Lhwyd (1703) and Linck (1674–1734), the students of Star-Fishes; Peyssonel (b. 1694), the investigator of Polyps and the opponent of Marsigli and Reaumur, who held them to be plants; Woodward, the palaeontologist (1665–1722)—not to speak of others of less importance. Two years after Ray's death Carl Linnaeus (1707–1778) was born. Unlike Jacob Theodore Klein (1685=1759), whose careful Linnaeus. treatises on various groups of plants and animals were published during the period between Ray and Linnaeus, the latter had his career marked out for him in a university, that of Upsala, where he was first professor of medicine and subsequently of natural history. His lectures formed a new departure in the academic treatment of zoology and botany, which, in direct continuity from the middle ages, had hitherto been subjected to the traditions of the medical profession and regarded as mere branches of " materia medica." Linnaeus taught zoology and botany as branches of knowledge to be studied for their own intrinsic interest. His great work, the Systema naturae, ran through twelve editions during his lifetime (1st ed. 1735, 12th 1768). Apart from his special discoveries in the anatomy of plants and animals, and his descriptions of new species, the great merit of Linnaeus was his introduction of a method of enumeration and classification which may be said to have created systematic zoology and botany in their present form, and establishes his name for ever as the great organizer, the man who recognized a great practical want in the use of language and supplied it. Linnaeus adopted Ray's conception of species, but he made species a practical reality by insisting that every species shall have a double Latin name —the first half to be the name of the genus common to several species, and the second half to be the specific name. Previously to Linnaeus long many-worded names had been used, sometimes with one additional adjective, sometimes with another, so that no true names were fixed and accepted. Linnaeus by his binomial system made it possible to write and speak with accuracy of any given species of plant or animal. He was, in fact, the Adam of zoological science. He proceeded further to introduce into his enumeration of animals and plants a series of groups, viz. genus, order, class, which he compared to the subdivisions of an army or the subdivisions of a territory, the greater containing several of the less, as follows: Class. Order. Genus. Species. Variety. Genus sum- Genus inter- Genus proxi- Species. Individuum. mum. medium. mum. Provincia. Territorium. Paroecia. Pagus. Domicilium. Legio. Cohors. Manipulus. Contubernium. Miles. Linnaeus himself recognized the purely subjective character of his larger groups; for him species were, however, objective: " there are, " he said, " just so many species as in the beginning the Infinite Being created." It was reserved for a philosophic zoologist of the 19th century (Agassiz, Essay on Classification, 1859) to maintain that genus, order and class were also objective facts capable of precise estimation and valuation. This climax was reached at the very moment when Darwin was publishing the Origin of Species (1859), by which universal opinion has been brought to the position that species, as well as genera, orders and classes, are the subjective expressions ofa vast ramifying pedigree in which the only objective existences are individuals, the apparent species as well as higher groups being marked out, not by any distributive law, but by the inter-action of living matter and its physical environment, causing the persistence of some forms and the destruction of vast series of ancestral intermediate kinds. The classification of Linnaeus (from Syst. Nat., 12th ed., 1766) should be compared with that of Aristotle. It Ciassifiis as follows—the complete list of Linnaean genera cation of being here reproduced:— Linnaeus. Class I. MAMMALIA. Order 1. Primates. Genera: Homo, Simia, Lemur, Vespertilio. 2. Bruta. Genera: Elephas, Trichecus, Bradypus, Myrmecophaga, Manis, Dasypus. Ferae. Genera : Phoca, Canis, Felis, Viverra, Mustela, Ursus, Didelphys, Talpa, Sorex, Erinaceus. Glires. Genera : Hystrix, Lepus, Castor, Mus, Sciurus, Noctilio. Pecora. Genera: Camelus, Moschus, Cervus, Capra, Ovis, Bos. Belluae. Genera: Equus, Hippopotamus, Sus, Rhinoceros. Cete. Genera : Monodon, Balaena, Physeter, Delphinus. Class II. AvES. Order i. Accipitres. Genera: Vultur, Falco, Strix, Lanius. 2. Picae. Genera: (a) Trochilus, Certhia, Upupa, Buphaga, Sitta, Oriolus, Coracias, Gracula, Corms, Paradisea; (b) Ramphastos, Trogon, Psittacus, Crotophaga, Picus, Yunx, Cucutus, Bucco; (c) Buceros, Alcedo, Merops, Todos. Anseres. Genera: (a) Anas, Mergus, Phaethon, Plotus; (b) Rhyncops, Diomedea, Alca, Procellaria, Pelecanus, Larus, Sterna, Colymbus. Grallae. Genera: (a) Phoenicopterus, Platalea, Palamedea, Mycteria, Tantalus, Ardea, Recurvirostra, Scolopax, Tringa, Fulica, Parra, Rallus, Psophia, Cancroma; (b) Hematopus, Charadrius, Otis, Struthio. Gallinae. Genera: Didus, Pave, Meleagris, Crax, Phasianus, Tetrao, Numida. 6. Passeres. Genera: (a) Loxia, Fringilla, Emberiza; (b) Caprimulgus, Hirundo, Pipra; (c) Turdus, Ampelis, Tanagra, MYluscicapa; (d) Pants, Motacilla, Alauda, Sturnus, Columba. Class Ill. AMPHIBIA. Order I. R.eptilia. Genera : Testudo, Draco, Lacerta, Rana. 2. Serpentes. Genera: Crotalus, Boa, Coluber, Anguis, Amphisbaena, Caecilia. Nantes. Genera: Petromyzon, Raja, Squalus, Chimaera, Lophius, Acipenser, Cyclepterus, Balistes, Ostracion, Tetrodon, Diodon, Centriscus, Syngnathus, Pegasus. Class IV. Pisces. Order 1. Apodes. Genera: Muraena, Gymnotus, Trichiurus, Anarrhichas, Ammodytes, Ophidium, Stromateus, Xiphias. 2. Jugulares. Genera: Callionymus, Uranoscopus, Trachinus, Gadus, Blennius. Thoracici. Genera: Cepola, Echeneis, Coryphaena, Gobius, Coitus, Scorpaena, Zeus, Pleuronectes, Chaetodon, Sparus, Labrus, Sciaena, Perca, Gasterosteus, Scomber, Mullus, Trigla. Abdominales. Genera: Cobitis, Amia, Silurus, Zeuthis, Loricaria, Selmo, Fistularia, Esox, Elops, Argentina, Atherina, Mugil, Mormyrus, Exocoetus, Polynemus, Clupea, Cyprinus. 3• 4. 5. 6. 7. 3• 4. 5. 3. 3. 4. Class V. INSECTA. Order I. Coleoptera. Genera: (a) Scarabaeus, Lucanus, Dermestes, Hister, Byrrhus, Gyrinus, Attelabus, Curculio, Silpha, Coccinella; (b) Bruchus, Cassida, Ptinus, Chrysomela, His pa, Meloe, Tenebrio, Lampyris, Mo>della, Staphylinus; (c) Cerambyx, Leptura, Cantharis, Elater, Cicindela, Buprestis, Dytiscus, Carabus, Necydalis, Forficula. 2. Hemiptera. Genera: Blatta, Mantis, Gryllus, Fulgora, Cicada, Notonecta, Nepa, Cimex, Aphis, Chermes, Coccus, Thrips. 3. Lepidoptera. Genera: Papilio, Sphinx, Phalaena. „ 4. Neuroptera. Genera: Libellula, Ephemera, Myrmeleon, Phryganea, Hemerobius, Panorpa, Raphidia. Hymenoptera. Genera: Cynips, Tenthredo, Sirex, Ichneumon, Sphex, Chrysis, Vespa, Apis, Formica, Mutilla. 6. Diptera. Genera: Oestrus, Tipula, Musca, Tabanus, Culex, Empis, Conops, Asilus, Bombylius, Hippobosca. Aptera. Genera: (a) Pedibus sex; capite a thorace discreto : Lepisma, Podura, Termes, Pediculus, Pulex. (b) Pedibus 8–14; capite thoraceque unitis: Acarus, Phalangium, Aranea, Scorpio, Cancer, Monoculus, Oniscus. (c) Pedibus pluribus; capite a thorace discreto: Scolopendra, lulus. Class VI. VERMES. Order 1. Intestina. Genera: (a) Pertusa laterali poro: Lumbricus, Sipunculus, Fasciola. (b) Imperforata poro laterali nullo: Gordius, Ascaris, Hirudo, Myxine. 2. Mollusca. Genera: (a) Ore supero; basi se afligens: Actinia, Ascidia. (b) Ore antico; corpore pertuso laterali foraminulo: Limax, Aplysia, Doris, Tethis. (c) Ore antico; corpore tentaculis antice cincto: Holothuria, Terebella. (d) Ore antico; corpore brachiato: Triton, Sepia, Clio, Lernaea, Scyllaea. (e) Ore antico; corpore pedato: Aphrodita, Nereis. (f) Ore infero centrali: Medusa, Asteria, Echinus. ^ 3. Teslacea. Genera: (a) Multivalvia: Chiton, Lepas, Pholas. (b) Bivalvia (= Conchae) : Mya, Solen, Tellina, Cardium, Mactra, Donax, Venus, Spandylus, Chama, Arca, Ostrea, Anomia, Mytilus, Pinna. (c) Univalvia spira regulari (= Cochleae) : Argonauta,, Nautilus, Conus, Cypraea, Bulla, Voluta, Buccinum, Strombus, Murex, Trochus, Turbo, Helix, Nerita, Haliotis. (d) Univalvia absque spira regulari: Patella, Dentalium, Serpula, Teredo, Sabella. • 4. Lithophyta. Genera: Tubipora, Madrepora, Millepora, Cellepora. 5. Zoophyta. Genera: (a) Fixata: Isis, Gorgonia, Alcyonium, Spongia, Flustra, Tubularia, Corallina, Sertularia, Vorticella. (b) Locomotiva: Hydra, Pennatula, Taenia, Volvox, Furia, Chaos. The characters of the six classes are thus given by Linnaeus: Cor biloculare, biauritum; Sanguine calido, rubro: Cor uniloculare, uniauritum; 1 2 Sanguine frigido; rubro: Cor uniloculare, inauritum; Sanie frigida, albida: 1 The anatomical error in reference to the auricles of Reptiles and Batrachians on the part of Linnaeus is extremely interesting, since it shows to what an extent the most patent facts may escape the observation of even the greatest observers, and what an amount of repeated dissection and unprejudiced attention has been necessary before the structure of the commonest animals has become known. Between Linnaeus and Cuvier there are no very great names; but under the stimulus given by the admirable method and system of Linnaeus observation and description From of new forms from all parts of the world, both Linnaeus recent and fossil, accumulated. We can only cite the to cuvter. names of Charles Bonnet (1720-1793), the entomologist, who described the reproduction of Aphis; Banks and Solander, who accompanied Captain Cook on his first voyage( 1768–1771); Thomas Pennant (1726–1798), the describer of the English fauna; Peter Simon Pallas (1741-181I), who specially extended the knowledge of the Linnaean Vermes, and under the patronage of the empress Catherine explored Russia and Siberia; De Geer (1720–1778), the entomologist; Lyonnet (17o7--1789), the author of the monograph of the anatomy of the caterpillar of Cossus ligniperdus; Cavolini (1756--18ro), the Neapolitan marine zoologist and forerunner of Della Chiaje (fl. 1828); O. F. Muller (1730-1784), the describer of fresh-water Oligochaeta; Abraham Trembley (1700–1784), the student of Hydra; and O. F. Ledermuller (1719–1769), the inventor of the term Infusoria. The effect of the Linnaean system upon the general conceptions of zoologists was no less marked than were its results in the way of stimulating the accumulation of accurately observed details. The notion of a scala naturae, which had since the days of classical antiquity been a part of the general philosophy of nature amongst those who occupied themselves with such conceptions, now took a more definite form in the minds of skilled zoologists. The species of Linnaeus were supposed to represent a aeries of steps in a scale of ascending complexity, and it was thought possible thus to arrange the animal kingdom in a single series—the orders within the classes succeeding one another in regular gradation, and the classes succeeding one another in a similar rectilinear progression. J. B. P. de Lamarck (1744–1829) represents most completely, both by his development theory (to be further Lamarck's mentioned below) and by his scheme of classifica- atesstfttion, the high-water mark of the popular but cation, fallacious conception of a scala naturae. His classification (1801–1812) is as follows: Invertebrata. 1. Apathetic Animals. Class I. INFUSORIA. Orders: Nuda, Appendiculata. Class II. PoLYPI. Orders: Ciliati (Rotifera), Denudati (Hydroids), Vaglnati (Anthozoa and Polyzoa), Natantes (Crinoids). Class III. RADIARIA. Orders: Mollia (Acalephae), Echinoderma (including Actiniae). Class IV. TUNICATA. Orders: Bothryllaria, Ascidia. Class V. VERMES. Orders: Molles (Tape-Worms and Flukes), Rigiduli (Nematoids), Hispiduli (Nais, &c.), Epitoariae (Lernaeans, &c.). 2. Sensitive Animals. Class VI. INSECTA (Hexapoda). Orders: Aptera, Diptera, Hemiptera, Lepidoptera, Hymenoptera, Neuroptera, Orthoptera, Coleoptera. Class VII. ARACHNIDA. Orders: Antennato-Trachealia (=Thysanura and Myriapoda), Exantennato-Trachealia, Exantennato-Branchialia. Class VIII. CRUSTACEA. Orders: Heterobranchia (Branchiopoda, Isopoda, Amphipoda, Stomapoda), Homobranchia (Decapoda). Class IX. ANNELIDA. Orders : A poda, Antennata, Sedentaria. Class X. CIRRIPEDIA. Orders : Sessilia, Pedunculata. Class XI. CONCHIFERA. Orders: Dimyaria, Monomyaria. Class XII. MOLLUSCA. Orders: Pteropoda, Gasteropada, Trachelipoda, Cephalopoda, Heteropoda. Vertebrata. 3. Intelligent Animals. Class XIII. FISHES. Class XV: BIRDS. , XIV. REPTILES. „ XVI. MAMMALS. 5. 7. ,, „ viviparis, Mammalibus; oviparis, Avibus. pulmone arbitrario, Amphibiis; branchiis externis, Piscibus. antennatis, Insectis; tentaculatis, Vermibus. The enumeration of orders above given will enable the reader to form some conception of the progress of knowledge relating to the lower forms of life during the fifty odd years which intervened between Linnaeus and Lamarck. The number of genera recognized by Lamarck is more than ten times as great as that recorded by Linnaeus. We have mentioned Lamarck before his great contemporary Cuvier because, in spite of his valuable philosophical doctrine of development, he was, as compared with Cuvier and estimated as a systematic zoologist, a mere enlargement and logical out-come of Linnaeus. The distinctive merit of G. L. Cuvier (1769–1832) is that he started a new view as to the relationship of animals, which he Cuvkr. may be said in a large measure to have demon- strated as true by his own anatomical researches. He opposed the scala naturae theory, and recognized four distinct and divergent branches or embranchemens, as he called them, in each of which he arranged a certain number of the Linnaean classes, or similar classes. The embranchemens were characterized each by a different type of anatomical structure. Cuvier thus laid the foundation of that branching tree-like arrangement of the classes and orders of animals now recognized as being the necessary result of attempts to represent what is practically a genealogical tree or pedigree. Apart from this, Cuvier was a keen-sighted and enthusiastic anatomist of great skill and industry.;, It is astonishing how many good observers it re-quires to dissect and draw and record over and over again the structure of an animal before an apps iximately correct account of it is obtained. Cuvier dissected many Molluscs and other animals which had not previously been anatomized; of others he gave more correct accounts than had been given by earlier writers. Another special distinction of Cuvier is his remarkable work in comparing extinct with recent organisms, his descriptions of the fossil Mammalia of the Paris basin, and his general application of the knowledge of recent animals to the reconstruction of extinct ones, as indicated by fragments only of their skeletons. It was in 1812 that Cuvier communicated to the Academy of Sciences of Paris his views on the classification of animals. He says: " Si Von considere le regne animal d'apres les principes que nous venons de poser, en se debarassant des prejuges etablis sur les divisions anciennement admises, en n'ayant egard qu' a I'organisation et a la nature des animaux, et non pas a leur grandeur, a leur utilite, au plus ou mains de connaissance que nous en avons, ni a toutes les autres circonstances accessoires, on trouvera qu'il existe quatre formes principales, quatre plans generaux, si l'on pent s'exprimer ainsi, d'apres lesquels tous les animaux semblent avoir ete rnodeles et dont les divisions ulterieures, de quelque titre que les naturalistes les aient decorees, ne sont que des modifications assez legeres, fondees sur le developpement, ou l'addition de quelques parties qui ne changent rien a l'essence du plan." Cuvk?s His classification as finally elaborated in Le Regne classification. .- catto Animal (Paris, 1829) is as follows: First Branch. Animalia Vertebrata. Class I, MAMMALIA. Orders: Biniana, Quadrumana, Carnivora, Marsupialia, Rodentia, Edentata, Pachydermata, Ruminantia, Cetacea. Class II. BIRDS. Orders: Accipitres, Passeres, Scansores, Gallinae, Grallae, Palmipedes. Class III. REPTILIA. Orders : Chelonia, Sauria, Ophidia, Batrachia. Class IV. FISHES. Orders: (a) Acanthopterygii, Abdominales, Subbrachii, A podes, Lophobranchii, Plectognathi; (b) Sturiones, Selachii, Cyclostomi. Second Branch. Animalia Mollusca. Class I. CEPHALOPODA. Class II. PTEROPODA. Class III. GASTROPODA. Orders: Pulmonala, Nudibranchia, Inferobranchia, Tecti- branchia, Heteropoda, Pectinibranchia, Tubulibranchia, Scutibranchia, Cyclobranchia. Class IV. ACE PHALA. Orders: Testacea; Tunicata. Class V. BRACHIOPODA. Class VI. CIRRIIOPODA. Third Branch. Animalia Articulata. Class I. ANNELIDES. Orders: Tubicolae, Dorsibranchiae, Abranchiae. Class II. CRUSTACEA. Orders: (a)' Malacostraca: Decapoda, Stomapoda, Amphipoda, Laernodipoda, Isopoda; (b) Entomostraca: Branchiopoda, Poecilopoda, Trilobitae. Class III. ARACHNIDES. Orders: Pulmonariae, Tracheariae. Class IV. INSECTS. Orders: Myriapoda, Thysanura, Parasita, Suctoria, Coleoptera, Orthoptera, Hemiptera, Neuroptera, Hymenoptera, Lepidoptera, Rhipiptera, Diptera. Fourth Branch. Animalia Radiata. Class I. ECHINODERMS. Orders: Pedicellata, Apoda. Class II. INTESTINAL WORMS. Orders: Neuzatoidea, Parenchymatosa. Class III. ACALEPHAE. Orders: Simplices, Hydrostaticae. Class IV. POLYPI (including the Coelentera of later authorities and the Polyzoa). Orders: Carnosi, Gelatinosi, Polypiarii. Class V. INFUSORIA. Orders: Rotifera, Homogenea (this includes the Protozoa of recent writers and some Protophyla). The leading idea of Cuvier, his four embranchemens, was con-firmed by the Russo-German naturalist Von Baer (1792–1876), who adopted Cuvier's divisions, speaking of them as von Baer. the peripheric, the longitudinal, the massive, and the vertebrate types of structure. Von Baer, however, has another place in the history of zoology, being the first and most striking figure in the introduction of embryology into the consideration of the relations of animals to one another. Cuvier may be regarded as the zoologist by whom anatomy was made the one important guide to the understanding of the relations of animals. But the belief, dating from Malpighi The mar-(167o), that there is a relationship to be "discovered, photo and not merely a haphazard congregation of varieties of structure to be classified, had previously gained ground. gtstB' Cuvier was familiar with the speculations of the " Natur-philosophen," and with the doctrine of transmutation and filiation by which they endeavoured to account for existing animal forms. The noble aim of F. W. J. Scheiling, " das ganze System der Naturlehre von dem Gesetze der Schwere bis zu den Bildungstrieben der Organismus als ein organisches Ganze darzustellen," which has ultimately been realized through Darwin, was a general one among the scientific men of the year 'Soo. Lamarck accepted the development theory fully, and pushed his speculations far beyond the realm of fact. The more cautious Cuvier adopted a view of the relationships of animals which, whilst denying genetic connexion as the explanation, recognized an essential identity of structure throughout whole groups of animals. This identity was held to be due to an ultimate law of nature or the Creator's plan. The tracing out of this identity in diversity, whether regarded as evidence of blood-relationship or as a remarkable display of skill on the part of the Creator in varying the details whilst retaining the essential, became at this period a special pursuit, to which Goethe, the poet, who himself contributed importantly to it, gave the name " morphology." C. F. Wolff, Goethe and Olsen share the credit of having initiated these views, in regard especially to the structure of flowering plants and the Vertebrate skull. Cuvier's doctrine of four plans of structure was essentially a morphological one, and so was the single-scale doctrine of Buffon and Lamarck, to which it was opposed. Cuvier's morphological doctrine received its fullest development in the principle of the " correlation of parts," which he applied to palaeontological investigation, namely, that every animal is a definite whole, and that no part can be varied without entailing correlated and law-abiding varia• tions in other parts, so that from a fragment it should be possible, had we a full knowledge of the laws of animal structure or morphology, to reconstruct the whole. Here Cuvier was imperfectly formulating, without recognizing the real physical basis of the phenomena, the results of the laws of heredity, which were subsequently investigated and brought to bear on the problems of animal stricture by Darwin. Sir Richard Owen (1804–1892) may be regarded as the fore-most of Cuvier's disciples. Owen not only occupied himself with the dissection of rare animals, such as the Pearly Owen. Nautilus, Lingula, Limulus, Prolopterus, Apteryx, &c., and with the description and reconstruction of extinct reptiles, birds and mammals—following the Cuvierian tradition—but gave precision and currency to the morphological doctrines which had taken their rise in the beginning of the century by the introduction of two terms, " homology " and " analogy," which were defined so as to express two different kinds of agreement in animal structures, which, owing to the want of such counters of thought," had been hitherto continually confused. Analogous structures in any two animals compared were by Owen defined as structures performing similar functions, but not necessarily derived from the modification of one and the same part in the " plan '' or " archetype " according to which the two animals compared were supposed to be constructed. Homologous structures were such as, though greatly differing in appearance and detail from one another, and though performing widely different functions, yet were capable of being shown by adequate study of a series of intermediate forms to be derived from one and the same part or organ of the " plan-form " or " archetype." It is not easy to exaggerate the service rendered by Owen to the study of zoology by the introduction of this apparently small piece of verbal mechanism ; it takes place with the classificatory terms of Linnaeus. And, though the conceptions of " archetypal morphology," to which it had reference, are now abandoned in favour of a genetic morphology, yet we should remember, in estimating the value of this and of other speculations which have given place to new views in the history of science, the words of the great reformer himself. " Erroneous observations are in the highest degree injurious to the progress of science, since they often persist for a long time. But erroneous theories, when they are supported by facts, do little harm, since every one takes a healthy pleasure in proving their falsity " (Darwin). Owen's definition of analogous structures holds good at the present day. His homologous structures are now spoken of as " homogenetic " structures, the idea of community of representation in an archetype giving place to community of derivation from a single representative structure present in a common ancestor. Darwinian morphology has further rendered necessary the introduction of the terms " homoplasy " and " homoplastic " (E. Ray Lankester, in Ann. and Mag. Nat. Hist. 187o) to express that close agreement in form which may be attained in the course of evolutional changes by organs or parts in two animals which have been subjected to similar moulding conditions of the environment, but have not a close genetic community of origin, to account for their similarity in form and structure, although they have a certain identity in primitive quality which is accountable for the agreement of their response to similar moulding conditions. The classification adopted by Owen in his lectures (1855) Owen's does not adequately illustrate the progress of zoological elassm- knowledge between Cuvier's death and that date, but, cation, such as it is, it is worth citing here. Province: Vertebrata (Myelencephala, Owen). Classes: MAMMALIA, AYES, REPTILIA, PISCES. Province: Articulata. Classes: ARACHNIDA, INSECTA (including Sub-Classes Myriapoda, Hexapoda), CRUSTACEA (including Sub-Classes Entomostraca, Malacostraca), EPIZOA (Epizootic Crustacea), ANNELLATA (Chaetopods and Leeches), CIRRIeEDIA. Province: Mollusca. Classes: CEPHALOPODA, GASTEROPODA, PTEROPODA, LAMELLIBRANCHIATA, BRACHIOPODA, TUNICATA. Province: Radiata. Sub-Province: Radiaria. Classes: ECHINODERMATA, BRYOZOA, ANTHOZOA, ACALEPHAE, HYDROZOA. Sub-Province: Entozoa. Classes: COELELMINTHA, STERELMINTHA. Sub-Province; Infusoria. Classes: ROTIFERA, POLYGASTRIA (the Protozoa of recent authors). The real centre of progress of systematic zoology was no longer in France nor with the disciples of Cuvier in England, but after his death moved to Germany. The wave of morphological speculation, with its outcome of new systems and new theories of classification (see Agassiz, Essay on Classification, 18J9), which were as numerous as the professors of zoological science, was necessarily succeeded in the true progress of the science by a period of minuter study in which the microscope, the discovery of embryological histories, and the all-important cell-theory came to swell the stream of exact knowledge. The greatest of all investigators of animal structure in the 19th century was Johann Muller (1801-1858), the successor in Muller. Germany of the anatomists Rathke (1793-1860) and Meckel (1781-1833). His true greatness can only be estimated by a consideration of the fact that he was a great teacher not only of human and comparative anatomy and zoology but also of physiology, and that nearly all the mostdistinguished German zoologists and physiologists of the period 185o to 187o were his pupils and acknowledged his leader-ship. The most striking feature about Johann Mailer's work, apart from the comprehensiveness of his point of view, in which he added to the anatomical and morphological ideas of Cuvier a consideration of physiology, embryology and microscopic structure, was the extraordinary accuracy, facility and completeness of his recorded observations. He could do more with a single specimen of a rare animal (e.g. in his memoir on Amphioxus, Berlin, 1844) in the way of making out its complete structure than the ablest of his contemporaries or successors could do with a plethora. His power of rapid and exhaustive observation and of accurate pictorial reproduction was phenomenal. His most important memoirs, besides that just mentioned, are those on the anatomy and classification of Fishes, on the Caecilians and on the developmental history of the Echinoderms. A name which is apt to be forgotten in the period between Cuvier and Darwin, because its possessor occupied an isolated position in England and was not borne up by any J. v. great school or university, is that of John Vaughan Thomp-Thompson (1779-1847), an army surgeon, who in 1816 son. became district medical inspector at Cork, and then took to the study of marine Invertebrata by the aid of the microscope. Thompson made three great discoveries, which seem to have fallen in his way in the most natural and simple manner, but must be regarded really as the outcome of extraordinary genius. He showed (1830) that the organisms like Flustra are not hydroid Polyps, but of a more complex structure resembling Molluscs, and he gave them the name Polyzoa He discovered (1823) the Pentacrinus europaeus, and showed that it was the larval form of the Feather-Star Antedon (Comatula). He upset (1830) Cuvier's retention of the Cirripedes among Mollusca, and his subsequent treatment of them as an isolated class, by showing that they begin life as free-swimming Crustacea identical with the young forms of other Crustacea. Vaughan Thompson is a type of the marine zoologists, such as Dalyell, Michael Sars, P. J. Van Beneden, Claparede, and Allman, who during the 19th century approached the study of the lower marine organisms in the same spirit as that in which Trembley and Schaffer in the 18th century, and Swammerdam in the 17th, gave themselves to the study of the minute fresh-water forms of animal life. It is impossible to enumerate or to give due consideration to all the names in the army of anatomical and embryological students of the middle third of the 19th century whose labours bore fruit in the modification of zoological theories and in the building up of a true classification of animals. Their results are best summed up in the three schemes of classification which follow below—those of Rudolph Leuckart (1823-1896), Henri Milne-Edwards (180o-1884), and T. H. Huxley (1825-1895), all of whom individually contributed very greatly by their special discoveries and researches to the increase of exact knowledge. Contemporaneous with these were various schemes of classification which were based, not on a consideration of the entire structure of each animal, but on the variations of a Single-single organ, or on the really non-significant fact of fact the structure of the egg. All such single-fact systems systems have proved to be departures from the true line of of cliasslgrowth of the zoological system which was shaping flcatloa itself year by year—unknown to those who so shaped it—as a genealogical tree. They were attempts to arrive at a true know-ledge of the relationships of animals by " royal roads "; their followers were landed in barren wastes. R, Leuckart's classification (Die Morphologie and Leuckart's die Verwandtschaftsverhaltnisse der wirbellosen Thiere, :LT Brunswick, 1884) cedoa. is as follows: Type 1. Coelenterata. Class I. POLYPI. Orders: Anthozoa and Cylicozoa. ,, II. ACALEPHAE. Orders: Discophorae and Ctenophore, • 1030 Type 2. Echinodermata. Class I. PELMATOZOA. Orders: Cystidea and Crinoidea. „ II. AcrieozoA. Orders: Echinida and Asterida. „ III. SCYTODERMATA. Orders: Holothuriae and Sipunculida. Type 3. Vermes. Class I. ANENTERAETI. Orders: Cestodes and Acanthocephali. „ II. APODES. Orders: Nemertini, Turbellarii, Tematodes and Hirudinei. „ III. CILIATI. Orders: Bryozoa and Rotif era. „ IV. ANNELIDES. Orders: Nematodes Lumbricini and Branchiati. Type 4. Arthropoda. Class I. CRUSTACEA. Orders: Entomostraca and Malacostraca. „ H. INSECTA. Orders: Myriapoda, Arachnida (Acera, Latta), and Hexapoda. Type 5. Mollusca. Class I. TUNICATA. Orders: Ascidiae and Salpae. „ II. ACEPHALA. Orders: Lamellibranchiata and Brachiopoda. ,, III. GASTEROPODA. Orders : Heterobranchia, Dermatobranchia, Heleropoda, Ctenobranchia, Pulmonata, and Cydobranchia. „ IV. CEPHALOPODA. Type 6. Vertebrata. (Not specially dealt with.) ,Milne- The classification given by Henri Milne-Edwards cciassiiri- (Cours Elementaire d'Histoire Naturelle, Paris, 1855) cation. is as follows: Branch I. Osteozoaria or Vertebrata. Sub-Branch I. Allantoidians. Class I. MAMMALIA. Orders: (a) Monodelphia: Bimana, Quadrumana, Cheiroptera, Insectivore, Rodentia, Edentate, Carnivora, Amphibia, Pachydermata, Ruminantia, Cetacea; (b) Didelphia: Marsupialia, Monotremata. ,, II. BIRDS. Orders : Rapaces, Passeres, Scansores, Gallinae, Grallae, Palmipedes. „ III. REPTILES. Orders: Chelonia, Sauria, Ophidia. Sub-Branch 2. Anallantoidians. Class I. BATRACHIANS. Orders: Anura, Urodela, Perennibranchia, Caeciliae. II. FISHES. Section I. Ossei. Orders: Acanthopterygii, Abdominales, Subbrachii, A podes, Lophobranchii, Pleclognathi. Section 2. Chondropterygii. Orders: Sturiones, Selachii, Cyclostomi. Branch II. Entomozoa or Annelata. Sub-Branch i. Arthropoda. Class I. INSECTA. Orders: Coleoptera, Orthoptera, Neuroptera, Hymenoptera, Lepidoptera, Hemiptera, Diptera, Rhipiptera, Anopleura, Thysanura. „ 11. MYRIAPODA. Orders: Chilognatha and Chilopoda. „ III. ARACHNIDS. Orders: Pulmonaria and Trachearia. „ IV. CRUSTACEA. Section I. Podophthalmia. Orders: Decapoda and Stomopoda. Section 2. Edriophthalmi. Orders: Amphipoda, Loemodipoda and Isopoda. Section 3. Branchiopoda. Orders: Ostracoda, Phyllopoda and Trilobitae. Section 4. Entomostraca. Orders: Copepoda, Cladocera, Siphonostoma, Lernaeida, Cirripedia. Section 5. Xiphosura. (The orders of the classes which follow are not given in the work quoted.) Branch III. Malacozoaria or Mollusca. Sub-Branch I. Mollusca proper. Class I. CEPHALOPODA. Class III. GASTEROPODA. II.
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