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Show 110 MR. W. S. KENT ON A NEW NUDIBRANCH. [Jail. 28, to the species 1 here introduce, it being the only one possessing a double row of branchial papillae down each side of the back. In the species recently obtained from the docks, and for which I here propose the name of Embletonia grayi, the branchial papillae are developed to a still further extent, three, in the adult specimens, entering on each side into the formation of the second anterior fasciculus*. The oral lobes, moreover, are highly developed, while in Embletonia pallida they are described as being small and indistinct. The lingual membrane, or odontophore, again, furnishes points of distinction, the median denticles surpassing the lateral ones in size more considerably than in E. pallida ; and the odontophore in this respect more closely approximates to that of Eolis nana. The number of lingual plates also exceeds that possessed by Embletonia pallida, being not fewer than thirty-five, while in the latter there are said to be but twenty-one. The colour of the little Mollusk is a semitransparent white, having the integument of the antero-dorsal region usually more or less sprinkled with minute ramifying pigment-cells of a blackish hue, these occasionally extending over the papillae. The eyes are deeply sunk beneath the integument, and situated, some distance apart, immediately behind the tentacula; in many instances these organs are scarcely discernible, more especially in those specimens wherein the superficial pigment-cells are greatly developed. It is particularly remarkable that this Nudibranch is a denizen of water containing but about one-third of the saline constituents of pure sea-water. Its habits are gregarious ; and its tastes appear to be eminently carnivorous, the luxuriant masses of Cordylophora lacustris clothing the submerged timber-balks in the docks proving a special attraction, and serving not only for the purpose of food, but also as a suitable nidus whereon to deposit its spawn. The ova, or spawn, on being extruded are enveloped in a gelatinous mucus, adherent at first to any object wherewith it may be brought into contact; this property, however, disappears after a brief exposure to the surrounding medium. The spawn masses are of an irregular oval form, each mass containing from five or six to as many as forty or fifty ova. On first leaving the egg the young are, in common with other Nudibranchiata, furnished with a delicate nautiloid shell, and propel themselves through the water with great activity by means of their ciliated lobes, or epipodia. Figs. 12 and 13 represent the animal about one month after quitting the egg; but further stages of development remain to be traced. The length of the adult animal varies from one to as much as three tenths of an inch, though the majority of the specimens examined have not exceeded that of two tenths of an inch. * One or two specimens have been met with having three papillae in the first anterior fasciculus also. The arrangement of the papillae also holds good in distinguishing this species from the Ccdliopcea bellula of D'Orbigny, figured and described in the ' Ma". de Zoologie' for 1837. |