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Rh and beautifully figured, it belongs to the genus which Lovén called Limnetis, and Lièvin called Hedessa. Both those names, therefore, are superseded by Müller's Lynceus, as limited by Leach. As a further consequence the family Limnetidæ must yield its name to Lynceidæ, which takes rank as a phyllopod family; while in the Cladocera the name Lynceidæ must be discarded in favour of a family Chydoridæ, Chydorus having been detached earlier than any other Cladoceran genus from that fruitful mother of genera, Müller's Lynceus.

Since there is reason to expect that the changes of nomenclature above introduced will not be greeted with any rapturous enthusiasm by all zoologists, it may be good policy to ward off the "precious balms" of rebuke by evidence that the changes are not unsupported by precedent. In 1865 Sars established a family Lyncodaphnidæ, which Lilljeborg still upholds. But already, in 1867, Norman and Brady had substituted for it the name Macrothricidæ, with the explanation: "Sars' name for this Family 'Lyncodaphnidæ,' not being derived from the typical genus of the Family, in accordance with the usually received rules of nomenclature, we have substituted for it that here employed." It may of course be urged that this was only a youthful delinquency on the part of two authors whose acknowledged eminence is of later date. But such an argument will fall very flat in face of the circumstance that G.O. Sars himself, with the openmindness habitual to him, has now accepted the name Macrothricidæ, using it prominently in his papers of 1900 and 1901 on South American Entomostraca. Some may even now prefer the scholarly emendation Macrotrichidæ, long ago proposed by Dr. E. v. Martens in the 'Zoological Record.' The common outcry, that there is no "compensation for disturbance" in these rearrangements of nomenclature, is itself very inconsiderate. There can never be any fixity until a settlement has been carried out on the thoroughgoing application of sound principle. In the present instance the student of Cladocera should feel himself in a very happy position. By obedience to law he is involved in nothing worse than the sacrifice of the name Lynceidæ in favour of Chydoridæ. If he persists in wrongfully retaining Lynceus as a Cladoceran genus, he must sacrifice for it Alona, Baird, instituted in 1843, which has not