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description and figures of the external characters are tolerably good, with the exception of what he says of a kind of collar, which he compares to the iron ferule on the handle of an awl, and represents as surrounding the orifices of the tubes. Rösel has here evidently seen the tentacular sheath in a semi-everted state, in which it presents somewhat the appearance he has described; and believing this to be a permanent character of his polype, has been thus led into error. He has witnessed the currents caused by the tentacular cilia, but has attributed them to water expelled from the mouth. A discovery by Rösel of much interest was that of certain little roundish bodies, about the size of the head of a pin, and of a yellowish colour, which, in the month of May, 1754, he found in the water of a neighbouring pond, and which, on being allowed to rest, emitted from various parts of their surface little plumes like those of his “Federbusch-polyp." Risel has described these little bodies under the title of “Der Kleinere Federbusch-polyp mit dem ballenförmigen Körper.” They are the young condition of the Polyzoon, for which Cuvier afterwards constituted a new genus, under the name of Cristatella. Linnaeus's grand invention of a binary nomenclature had now been established, and we accordingly find in the tenth edition of the ‘Systema Naturae, published in 1758, the freshwater Polyzoa for the first time designated by a generic and specific name." The “Federbusch-polyp” of Rösel is here described under the title of Tubipora repens, but with Baeck erroneously referred to among the synonyms. In the “Fauna Suecica,’ 1761, we find the same animal mentioned under the same name.t. In 1766, Pallas published his ‘Elenchus Zoophytorum.'t In this work we have the fresh-water Polyzoa described under generic and specific names, in accordance with the example already set by Linnaeus. Under the genus Tubularia, Pallas includes two fresh-water Polyzoa; one is the “Polype à Panache” of Trembley, which is now described by Pallas under the name of Tubularia crystallina ; the other, the “Federbusch-polyp” of Rösel, described under that of Tubularia gelatinosa. In the year 1768, Pallas presented to the Royal Academy of Sciences of St. Petersburg, a memoir on a peculiar production which he had discovered in a lake connected with the River Kliasma, near Vlademir, in Russia. § It was in the form of large fungoid or spongy masses, and was composed of multitudes of closely compacted tubes, each of which opened upon the surface of the mass by a pentagonal or hexagonal orifice, which allowed of the exsertion of a polypoid body in all respects resembling those of Trembley and Rösel. To his newly discovered animal, Pallas gave the name of Tubularia fungosa ; it is identical with that subsequently named Alcyonella stagnarum by Lamarck. The memoir is illustrated by a plate exhibiting the external characters of the Polyzoon, and a magnified but not very correct view of the tentacular crown, and, though quite destitute of anatomical detail, must yet be viewed as an important contribution to the zoology of the day. Leendert Bomme, of Flissingen, in 1769, described the tentacular currents in certain

* LINNAEus, ‘Systema Naturae,” editio decima. Holmiae, 1758, vol. i., p. 790. t LINNAEUs, ‘Fauna Suecica.’ Stockholmiae, 1761, p. 537. : PALLAs, ‘Elenchus Zoophytorum.’ Hagae-Comitum, 1766. § PAllAs, Descriptio Tubulariae fungosae prope Volodemirum observatae. “Nov. Comm. Petr., xii, p. 565.

marine Polyzoa, and detected the cilia by whose action these currents were produced;" he observed similar currents, and the cilia causing them, in some fresh-water Polyzoa which he found in the Isle of Walcheren. We have seen that Trembley ascribed the currents in question to the motion of the tentacula, while Rösel, on the other hand, attributed them to the water ejected from the mouth. Leendert Bomme has the credit of referring them to the true cause; while in this discovery he has effected an important extension of our acquaintance with vibratile cilia, organs which had previously not been known beyond the Infusoria and Rotifera, and which have since been recognised as so very widely distributed, and so intimately connected with some of the most important functions of living beings. In the ‘Vermium terrestrium et fluviatilium Historia,’ published in 1773,t Müller institutes the name of Tubularia repens for the “Kammpolyp” of Schäffer, which he considers specifically distinct from the “Federbusch-polyp” of Rösel, chiefly on the grounds of its being deprived of the collar, which, as we have already seen, Rösel has erroneously attributed to his animal. Müller has distinctly traced with Trembley and Baker an oesophagus, stomach, and intestines, and has pointed out the error of Rösel regarding the statoblasts, which this naturalist mistook for the seeds of Lemna. In September, 1774, Blumenbach described, at a meeting of the Royal Society of Göttingen, a new fresh-water Polyzoon, which he had discovered in the neighbourhood of that town. He names it Tubularia sultana, and gives a figure of it in his ‘Manual of Natural History,’ published in 1779.S. It is at once distinguished from all previously described freshwater Polyzoa by the tentacula being disposed in a circle, instead of presenting the form of a crescent, by which the others are all characterised. Blumenbach's Tubularia sultana is the Polyzoon afterwards discovered by Gervais at Plessis-Piquet, near Paris, and for which this naturalist found it necessary to constitute a new genus under the name of Fredericella. Blumenbach characterises it in his manual as “Tubularia crista infundibuliformi, ad basin ciliata;” the latter part of this diagnosis can scarcely refer to the true vibratile cilia which clothe the tentacula in their entire length, and is apparently framed from an imperfect observation of the caliciform membrane with which the base of the plume is furnished, and whose deeply festooned margin may have suggested the character “ciliata.” In 1776, Eichhorn published his ‘Beiträge zur Naturgeschichte der Kleinsten Wasserthiere." In this we have a description with figures of a fresh-water Polyzoon, which he calls “Der Polyp mit dem Feder-busch.” Eichhorn's animal would seem to be the attached form of Plumatella repens, and identical with Schäffer's. He represents a specimen extending over

* LEENDERT BoMME, “Bericht aangaande verscheiden zoonderlinge Zee-Insecten.” Acta Vliss., 1769.

+ Müller, ‘Vermium terrestrium et fluviatilium Historia.” Lips., 1773.

f BLUMENBAch, Von den Federbusch-polypen in den Göttingeschen Gewässern. “Göttin. Mag.,’ i, p. 117.

§ BLUMENBAch, “Handbuch der Naturgeschichte.” Göttingen, 1779.

| Eichhor N, ‘Beiträge zur Naturgeschichte der kleinsten Wasserthiere in den Gewässern und um Danzig.” Danz., 1776.

an aquatic stem, and gives a tolerably good view of the expanded plume. He describes and figures the tentacular cilia. He tells us that each tentacle is furnished on the extremity with a depression, which he compares to the nail of the finger. This, however, is evidently the result of an erroneous interpretation of the appearance presented when the curved extremity of the tentacle is turned towards the eye of the observer and fore-shortened. So impressed, however, is he with the resemblance of the tentacle to a finger, that he says the animal may be called “Das Finger-thier,” and he is in great delight at seeing one of the supposed fingers when separated from the plume swimming about with an apparently spontaneous motion. Dumortier and Van Beneden inform us” that Schmiedel, in his “Icones plantarum, describes and figures, under the name of Spongia lacustris, the Alcyonella in the condition in which it is found in the autumn after the soft parts have disappeared. The “Icones plantarum' was published in 1782. I have not succeeded in procuring it. In 1786, was published the ‘Animalcula Infusoria’t of Müller. In this work is described, under the name of Leucophra heteroclita, a minute animal of whose identity with the ciliated embryo of Alcyonella fungosa, as subsequently pointed out by Meyen, or more probably with that of Plumatella repens, there can be now no doubt. Müller's description is accompanied by figures, very good considering the imperfect construction of the microscopes then available. In 1789, we find Bruguière, in the ‘Encyclopédie Methodique, describing, under the name of Alcyonium fluviatile, a production sent to him by M. Dantic, who found it in the waters of the fountain of Bagnolet, near Paris. Bruguière was evidently unacquainted with the memoir of Pallas, but his account leaves us in no doubt of the identity of his Alcyonium fluviatile with the Tubularia fungosa of this naturalist. His figure, however, is singularly incorrect; he represents the animal with a variable number of attenuated filiform tentacula, each terminated by a spherical capitulum, and the whole springing from about seven eighths of the circumference of a circular disc. In his location of the Polyzoon among the Alcyoniums, he errs too, as much as Pallas did when he made it a species of Tubularia. In 1797, Lichtenstein, believing that he had witnessed certain Polyzoa escaping from the little spherical capsules which occur imbedded in the base of Spongilla, maintained, in a communication to the Natural History Society of Copenhagen, that the fresh-water sponge consisted only of the cells of these Polyzoa after having been abandoned by the polypides;S an opinion which could only have arisen from some very confused observations, and probably from his having mistaken a dead Alcyonella for a Spongilla. He further maintains that all the forms of fresh-water Polyzoa then known are only variations of one and the same species. Hitherto, no step of importance had been made towards the scientific classification of the fresh-water Polyzoa. The invention by Linnaeus of a binary nomenclature, had, it is true,

* DuMoRTIER et VAN BENEDEN, Hist. Nat. des Polypes Comp. d’eau douce. “Nouveaux Mémoires de l'Acad.-Roy. de Bruxelles,’ tome xvi, 1843. f Otho FRIDERicus Müller, ‘Animalcula Infusoria Fluviatilia et Marina.' Hauniae, 1786. f BRUGUIERE, ‘Encycl. Method.” Vers, p. 24. § LichteNstein, ‘Skrivter of Naturhistorie Selkabet, p. 104. Kiobenhavn, 1797.

prepared the way for a systematic arrangement; but, as yet, the Polyzoa of fresh water had been placed in the same genera with marine forms of a totally different organization, while some of them had not been accurately distinguished from one another. At length, Cuvier, in his ‘Tableau Élémentaire des Animaux,” struck by the distinctive characters of the little Polyzoon described by Rösel, under the name of “Der Kleinere Federbusch-polyp mit dem ballen-formigen Körper,” assumed it as the type of a new genus, to which he gave the name of Cristatella. The other fresh-water Polyzoa he allowed to remain in the genera in which his predecessors had placed them, and even with regard to his Cristatella, though he acknowledge its affinity with the other fresh-water Polyzoa, he was ignorant of its true relations, for he kept it in the vicinity of the infusorial Vorticellae. In the year 1804, Vaucher published, in the ‘Bulletin de la Société Philomathique,” a short description of two Polyzoa, one of which he believes to be the animal described by Schäffer (Tubularia repens, Müller); the other a new species to which he gives the name of Tubularia lucifuga.t Waucher's memoir is accompanied by figures of both species, but the description is so meager, and the figures so defective, that it is impossible to determine the species intended. The memoir of Waucher was followed by a most important reform. Bosc, already convinced, that the so-called Tubularias of fresh water were incorrectly associated with the marine group of this name,t now constituted for their reception a distinct genus, whose characters he gave in the same number of the ‘Bulletin’ as that which contained Waucher's memoir. The following are the characters on which Bosc founded his new genus: “Polypier fixe a tige grèle, membraneux, souvent ramifié, terminé, ainsi que ses rameaux par un polype dont le corps peut entrer entièrement dans la tige, et dont la bouche est entourée d'un seul rang de tentacules ciliés.” Bosc, however, though he defined the genus, neglected to name it, and his views received but little attention till Lamarck, in his ‘Histoire des Animaux sans Vertèbres, published in 1816, gave the name of Plumatella to the genus defined by Bosc ; while, for the Alcyonium fluviatile of Bruguière, he constituted a new genus under the name of Alcyonella. In his definition of the genus Alcyonella, Lamarck has evidently been led into error by the description and figures of Bruguière, for the celebrated author of the ‘History of Invertebrate Animals, though he had seen recent specimens, seems to have examined them very imperfectly, and to have taken for granted the correctness of the account in the “Encyclopédie.’ He describes the polypes as “elongali cylindrici; tentaculis circa orem 15 ad 20, erectis, fasciculum turbinatum vel infundibuliformem uno latere imperfectum componentibus.” To Lamarck, however, notwithstanding the erroneous characters in this definition, is due the credit of having been the first to distribute the fresh-water Polyzoa under three distinct and peculiar genera, namely, Cristatella, Alcyonella, and Plumatella, a most important step towards the further elucidation of the tribe. Lamarck associates Cristatella and Alcyonella with Difflugia, a Rhizopod previously described by M. Leclerc, and with Spongilla, to constitute, under the name of “Polypiers fluviatiles,” the first section of his “Polypes & Polypier ;"

* CUVIER, ‘Tableau Élémentaire de l’histoire naturelle des Animaux.’ Paris, 1798.
+ VAUchER, Observations sur les Tubulaires d’eau, douce. “Bull. Soc. Philom.,’ 1804, p. 157.
: Bosc, ‘Histoire Naturelle des Vers.”

while Plumatella is united with Tubularia and Cellaria, and many other marine Hydrozoa and Polyzoa, to form, under the name of “Polypiers vaginiformes,” the second section of the same order. Lamarck enumerates four species of Plumatella, namely, P. cristata = “Polype a Panache,” Trembley; P. campanulata = “Federbusch-polyp,” Rösel; P. repens = Kammpolyp,” Schäffer; and P. lucifuga, Vaucher. The specific name of fluviatile given by Bruguière to the only species of the genus Alcyonella, at that time known, was changed by Lamarck into stagnarum, a name certainly more in conformity with the habits of the animal, but one far less expressive than the original name of fungosa given by Pallas, a name which, independently of its appropriateness, ought, in accordance with the rules of priority, and in justice to the memory of Pallas, to be still preserved. In his ‘Histoire des Polypiers,” published in 1816, Lamouroux changes Lamarck's name of Plumatella into that of Naisa, a change entirely uncalled for, and founded on erroneous views of the structure of the genus; and though Lamouroux retains the name of Naisa in his * Exposition Méthodique,'t published in 1821, Deslongchamps is the only other naturalist I can find who has thought it necessary to adopt it.} With the exception of the observations made by Trembley on his “Polype à Panache,” when he described a complete alimentary canal and retractor muscles, those by Baker, who gives an exceedingly correct account of the digestive tube in his “Bell-flower animal,” and those by Müller, who correctly describes the same parts in his Tubularia repens, though he has left us no figure, we find, up to the period of which we now write, no remark of any value on the internal structure of the fresh-water Polyzoa. In the year 1828, however, the attention of naturalists was called to the structure of these animals in a most elaborate memoir published by Raspail, under the title of ‘Histoire Naturelle de l'Alcyonella fluviatile.'S Raspail had, a short time before, in conjunction with M. Robineau Desvoidy, presented to the Academy of Sciences at Paris, a memoir on the same animal. This memoir, for a knowledge of which we are solely indebted to Cuvier's report|||—for it was never published— contains a most erroneous view of the subject, and maintains that the so-called polypes have no necessary connection with the sponge-like mass of the Alcyonella, and are merely accidental occupants of the cells. In the second memoir, however, the author entirely abandons his former opinion. This memoir is characterised by much originality, and, like most of the writings of Raspail, is marked by a complete freedom from the restraints which the authority of previous investigators so generally imposes. Many of his observations, however, are evidently made with inferior instruments, and the memoir is full of hasty generalisations, which the author builds on a far too limited number of facts. Raspail has detected the mouth and anus of Alcyonella; but though he has had the advantage of the previous observations of Trembley, Baker, and Müller,

* LAMouroux, ‘Histoire des Polypiers Coralligênes flexibles.” Caen, 1816.

+ LAMoU Roux, ‘Exposition Méthodique des genres de l'ordre des Polypiers.’ Paris, 1821.

f DesLongch AMPs, ‘Encyclopédie Méthodique, Zoophytes,’ 1824.

§ Raspail, Histoire Naturelle de l'Alcyonelle fluviatile et des genres voisins. Mém. de la Soc. d'Hist. Nat. de Paris,’ iv., 1828.

| Cuvier, ‘Hist, des progrès des Sci. Nat,’ tome ii.

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