An Attempt to re-classify the Rotifers

FIVE-AND-FORTY years have elapsed since Ehrenberg published his classification of the Rotifera, and his system still holds its ground. The mere statement of the fact is high praise; for what have not classifiers altered, and attempted to alter, during the last half century ? Not that his classification has escaped challenge. It was sharply criticised in the ' Histoire naturelle des Zoophytes*by Dujardin, in 1841; and the author showed by his criticism that he would probably have invented an excellent classification, if he had only had the requisite knowledge. For his arrangement of the Rotifers into great groups was excellent, and he failed in his subdivisions, obviously from lack of personal acquaintance with the creatures he was classifying. Leydig, also, in his admirable treatise ' Ueber den Bau und die systematische Stellung der Raderthiere/ in 1854, pointed out some of the obvious faults of Ehrenberg's system; and substituted for it a far inferior one of his own. Lastly, Dr. Samuel Bartsch, in a pamphlet on 'Die Raderthiere ' in 1870, and again in a larger treatise on the ' Rotatoria Hungarise' in 1877, has essayed a new classification, which is, I think, by no means a success. I propose now to point out, as briefly as may be, what seem to me to be the chief faults in these four systems; and then, availing myself of all that has been already done, to see how far the accumulated observations of the last forty-five years will enable us to arrange the Rotifers in well-marked and fairly natural groups. I am sanguine enough to think that this can be doae with a large proportion of them ; though there may remain outstanding some genera, that can at the best have only