BY
MARCUS HARTOG, M.A., Trinity College (D.Sc. Lond.)
Professor of Natural History in the Queen's College, Cork.
CHAPTER VIII
ROTIFERA, GASTROTRICHA, AND KINORHYNCHA
ROTIFERA—HISTORY—EXTERNAL FEATURES—MOVEMENT—ANATOMY—REPRODUCTION—EMBRYOLOGY—CLASSIFICATION—DISTRIBUTION—AFFINITIES—GASTROTRICHA—KINORHYNCHA
The Rotifera are microscopic animals, the largest not exceeding one-eighth of an inch in length. According to Hudson and Gosse,[[233]] they are first recorded in an observation of the Rev. John Harris, in 1696, of "an Animal like a large Maggot which could contract itself into a Spherical Figure, and then stretch itself out again; the end of its Tail appeared with a Forceps like that of an Ear-wig."[[234]] This was certainly a Bdelloid Rotifer.
In 1703 Leeuwenhoek[[235]] gave a fuller description of a tubicolous form, probably Limnias, and noted the peculiar appearance of the ciliary wreath as "two wheels thickset with teeth as the wheel of a watch." He also noted a little later[[236]] the way in which Melicerta (see p. [206]) builds its tube, and was the first to observe the revivification of certain species after drying.[[237]] Joblot, a French professor of mathematics, in 1718 figured and described a large number of new genera and species with more or less fantastic details. Baker's figures[[238]] are a considerable advance on Joblot's, and his descriptions of habits are still fresh and accurate. Eichhorn found a number of new and interesting forms; and O. F. Müller, influenced by the new discipline of Linnaeus, not only figured many species, but gave good short diagnoses of their characters. Ehrenberg in 1838 brought out his magnificent Infusionsthierchen, which contains descriptions and figures of what are now divided into Protophyta, Protozoa, Rotifera, and Gastrotricha. Dujardin's monograph on the "Infusoires," in the Suites à Buffon,[[239]] was in several respects an advance on Ehrenberg, whose power of observation was so great as to render his mistakes the more inexplicable. But Ehrenberg ever adhered to his errors as firmly as to his facts.
The occurrence of Rotifers among microscopic plants induced the botanists Cohn and Williamson[[240]] to work at their structure; the group has been studied by men engrossed in other professional cares, such as Gosse, Bedwell, Moxon, Rousselet, and Maupas. Huxley,[[241]] Leydig,[[242]] and Cohn[[243]] studied Rotifers in the '50's and early '60's with a precision the more remarkable when we remember the imperfect methods then available. This period was closed by the valuable monograph published in Arlidge's (4th) edition of Pritchard's Infusoria,[[244]] under the supervision of W. C. Williamson. Leidy began the study of the American Rotifers. Eckstein[[245]] gave a careful and interesting account of the species about Giessen in a richly illustrated paper. In recent times the modern methods of histological and embryological research have been applied by Vallentin,[[246]] Plate,[[247]] Tessin,[[248]] and Zelinka,[[249]] the three Studien ueber Rotatorien of the last author being indispensable to every student, and containing a full bibliography.
Hudson and Gosse's Monograph (1886-89) contains a history of the class to which, as to the whole book, we are deeply indebted; and a full systematic account of all published species.[[250]] C. Rousselet has introduced a method[[251]] of preparation of Rotifers in microscopic slides which enables workers to preserve the types they figure and describe for future identification and comparison. Gunson Thorpe has collected and studied Rotifera in China and Australia. It would be unfair not to record here the invaluable services of the late Thomas Bolton, and his son of the same name, both of Birmingham, and of J. Hood of Dundee, who have found and widely distributed living specimens of new, rare, and interesting species.