438 ME. p. W. BASSETT-SMITH ON [Apr. 18, The following papers were also read : — 1. A Systematic Description of Parasitic Oopepoda found on Fishes, with an Enumeration of the known Species. By P. W. Bassett-Smith, StafP-Surgeon R.N., F.Z.S., F.R.M.S. [Eeceived March 1, 1899.] (Plate XXVI.) The number of known Copepoda parasitic upon fishes has been gradually increasing of late years : and their peculiar modes of life, exti-aordinary forms, and the remarkable positions in which they are found have caused them to be an interesting study to those naturalists who are working in marine zoology, especially if they have been in the habit of handling fishes when recently caught. Prom a morphological point of view the lower types are the more interesting, as exemplifying the effect of parasitism on the females, which lose more and more their ordinary appendages, becoming nothing better than fixed saccular animals, capable of imbibing nourishment and producing progeny ; while the male, though often of very minute size, retains its general crustacean appearance. These points have repeatedly been investigated by Carl Vogt, Kurz, Glaus, and others. The literature on the subject is widely scattered, and many of the animals have exceedingly long lists of synonyms. Ifc has been my object in this paper, which I trust will be of use to future workers, to gather together this material, and to put it into a workable form, as a basis for further investigation. The latest attempt to systematize this group was made by A. Gerstacker in Bronn's ' Class, und Ordn. des Thier-reichs,' 1866-1879, Crustacea, vol. v., Copepoda, which admirable work I have followed very closely, excepting in some groups which are mentioned later on. He has very largely based his classification on the structure of the articulate organs, which appears to be the most certain and scientific method. As the more lowly organized groups are reached, viz., those in which the female has lost almost all its articulate appendages, the characters and conformation of the males become most valuable guides : these being often very minute or pigmy-like. In many cases they are quite unknown, and are therefore a good field for further work, the discovery of new forms being very pleasing. There is no doubt that continued research, especially on the non-edible fish, in different parts of the world, would be rewarded by the discovery of a great number of new forms, and, what is badly wanted, further specimens to establish genera, many of which have been recorded by a single observer onlv, and not infrequently from one specimen only. In a large number of cases the descriptions and plates found in the older works are most indefinite, making the diagnosis of the
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