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Show 328 MR. R. COLLETT* ON CERTAIN GOBIOID FISHES. [Mar. 5, the shape of a short black stripe ; this is the most conspicuous and durable of all the rows, and is never wanting. The caudal fin has a brownish shade ; sometimes this is also the case with the anal fin, whilst all the other fins are hyaline. The iris is silver-coloured, with black pupil; the upper margin of the eye is golden, which, after death, changes to a black. The younger individuals are more sparingly pricked; the row along the anal fin is the first which shows itself, and is already visible in the young ones, with a total length of 13 millims., where all the other pricks are wanting. In the males in full breeding almost every part of the body has a faint brownish light, although this is nowhere collected into larger dots, but is most distinct along the transverse impressions of the muscles. C. Habits and Distribution. Generation.-It is probable that no specimen lives more than one year, and after the close of the breeding-time dies without living through another spawning; consequently these fishes are really annual vertebrates. The spawning-season occurs in the Christiania Fjord in the summer months. The latest date at which I have found females with ripe spawn was on August 2, 1872, although the greater number of them had then already spawned. The normal period of spawning is the end of June or the beginning of July. On the 10th and 14th of August, 1875, I found them in the middle of their breeding, although several were still not quite mature. When the spawning is finished all the specimens disappear entirely, and become apparently extinct. The first young ones I took on August 28, 1875, when their average size was 22 millims.; a few specimens were rather larger (attaining about 30 millims.), or less (down to 13 millims.). At the same time there is not a single specimen of a greater size to be found at those places where they, in the middle of June, were found in numbers and only in a full-grown state. A month later the median length may be estimated at 34 millims., in the end of October at 38 millims. The development proceeds tolerably even with them all; and specimens are very rarely to be found which differ to any degree from the medium size. Most of the individuals attain their full size as early as December or January, in order that, when the organs of generation begiii to develop themselves in the following spring, they may acquire greater plumpness and strength in all parts of the body-a change which, as we have indicated above, chiefly takes place in the males. Amongst the thousands of specimens which I have examined during the autumn and winter, I have not found a single specimen with the slightest trace of the long teeth that, characterize the mature male ; and during the summer time all the males, without exception obtain these teeth. In the young females, at the age of only four months, the ovaries may be seen through the transparent body in the form of two elongated strings, filled with clear eggs; in the spawning-season these |
