OCR Text |
Show 1878.] MR. R. COLLETT ON CERTAIN GOBIOID FISHES. 337 tendency to division of the rays is characteristic of this species compared with Latrunculus pellucidus, in which division of the rays takes place especially in the ventral fins. The funnel is comparatively short; when closed it is, even in the male, removed from the vent to a distance about equal to its own length. In young males the ventral fins are very small, and their funnel-like shape is almost imperceptible, the connecting membrane being incomplete. In the female the ventral fins are completely rudimentary, being only present as a couple of two disconnected and very short rays scarcely the diameter of the eye in length. The mucous glands, which in L. pellucidus form so extensive a system, seem to be almost entirely wanting in Crystallogobius nilssonii ; in none of the specimens which I have examined have I been able, with certainty, to find a single complete row of such glands, either on the head or on any other part of the body. The skin.-No trace of scales has hitherto been detected in any of the specimens examined. As is the case in L. pellucidus, the whole side of the body shows a row of transverse impressions ; when examined in the microscope, no trace is found of follicles to which lost scales may have been attached; and it is therefore scarcely to be doubted that the body is altogether naked in this species. The number of these muscular impressions is twenty-seven, twenty of which have their place behind the vent; they bend together into the form of an angle in the middle line of the body, and denote exactly the number and size of the vertebrae. An actual lateral line, with open pores, does not exist. The colour.-As is the case in L. pellucidus, the body during life is transparent, with a faint bluish tinge, thereby enabling the vertebrae, the apple of the eye, &c. easily to be seen. The coloration of the skin is very faint, and does not vary in this respect to any degree, even during the spawning-season. The eyes are strongly coloured, their upper edge being of a shining metallic lustre (black after death) ; the iris is silvery. A well-defined blackish spot is found at the point of the lower jaw ; another black stripe stretches along the throat towards the ventral fins. At the root of each ray in the anal and the caudal fin there is a black point; these together form a continuous and distinct row, which is present in both sexes and at all ages; along the dorsal fin there is found a somewhat fainter row of brownish points, which is indistinct, or nearly wanting, in the female. Moreover all the rays are covered with minute blackish points. The body itself is almost unspotted (whitish when preserved in spirits), except on the sides of the belly, where a row of fine brownish spots stretches itself; these spots are largest and most distinct in the breeding female, their number being 3-5 on each side. C. Habits and Distribution. Generation.-With regard to the time of breeding and its duration, nothing conclusive can be said at present on account of the very PROC. ZOOL. Soc-1878, No. XXII. 22 |