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Show 366 MR. F. E. BEDDARD ON THE STRUCTURE [May 6, of the Serolidae and the Cymothoidae, which was published in the ' Transactions.' The present paper is a continuation of the same subject, but deals with the genus Arcturus. The material, like that of my former paper, consists of teased preparations and of sections of the eyes of species obtained during the voyage of H.M.S. 'Challenger,' all of which species have been described by me in m y Report (3). In m y paper on the structure of the eye in the Cymothoidae, I mentioned the principal papers dealing with the Isopodan eye, which are not many in number. Since the appearance of that paper but little has been published upon the Isopodan eye. I am, indeed, only acquainted with a single memoir upon the subject, one by Mr. S. Watase (11); this paper deals largely with Serolis, but it contains also some very weighty observations upon the morphology and pedigree of the Arthropod eye in general. It is gratifying to me personally to find that Mr. Watase has " verified all the chief results " of m y own research. This fact also gives me greater confidence in laying the present paper before the Society. If the state of preservation of the specimens of Serolis was so good as to enable me to state accurately the principal facts in the anatomy of the eye, it seems likely that the Arcturi, which were preserved in an identical fashion, will also furnish reliable data. In any case our knowledge of this particular genus is at present, so far as I am aware, absolutely nil; and it is almost unnecessary to state that the deep-sea forms are as little known as those which inhabit the shallower waters. Mr. Watase, in his description of the eye of Serolis, which occupies the first five pages of the special part, refers to the presence of a "corneagen" 1 (a term introduced by Patten, 13) below the cornea and above the cells of the vitrella; he also figures a row of pigmented cells surrounding the vitrella2. These structures were not figured or described by myself, but I am not prepared to dispute the probable justice of Mr. Watase's addition to m y own account. It seems to me to be very probable that this corneagen layer is, as Patten has particularly insisted, always present in eyes of these types ; and Watase has shown a very strong raison d'etre for its presence. The present paper, however, only professes to be a very small contribution to the morphology of the Isopodan eye; the main object is to compare the minute structue of the eye of species living in shallow water with that of their deep-sea allies. The questions involved are interesting and lead to some rather important conclusions about the life of these deep-sea forms. In the first part of m y ' Challenger ' Report, dealing ouly with the very remarkable genus Serolis (2), I gave some figures and a brief description of the structure of the eyes in two deep-sea species, viz. Serolis bromleyana and Serolis neara. Without recapitulating all the results here, I may point out that the eyes in those forms showed very considerable traces of degeneration ; this degeneration was 1 PI. xxix. fig. 1 eg, fig. la a. 2 This term was introduced by Lankcster and Bourne. |