OCR Text |
Show 1878.] MR. R. COLLETT ON CERTAIN GOBIOID FISHES. 333 males. Although the total length is almost the same as in many of the mature males (36-37 millims., in a single specimen 39 millims.), their body is so slender and their weight so inconsiderable, that two full-grown females, with the ovaries filled with ripe eggs, were not able to weigh down one large full-grown male. The head is pointed, with short jaws, which are straight and perfectly toothless, and are wanting the males' prominent projection on the intermaxillary bone. The first dorsal and the ventral fins are rudimentary (at a superficial glance they appear to be entirely wanting) ; the pectoral fins are certainly developed, but very short. The ovaries project far behind the vent on each side of the anal fin. The young females, with a total length of 30-33 millims., and with the ovaries filled with unripe eggs, have the body very slender and pointed : as in the old female the jaws are toothless, the first dorsal and the ventral fins apparently wanting. The young during growth.-The few young with a total length of about 25 millims. that have been at m y disposal have all been males. This is shown by the first traces of teeth, by the want of the long ovaries, as well as by the presence of all the fins ; certainly the first dorsal and the ventrals are short, but never wanting or even rudimentary. These fins may already be seen in the young with a total length of 21 millims., the smallest specimen I have found ; in this one, however, there was not yet any trace of the pectorals. It may therefore be supposed that in the males the first dorsal and the ventral fins spring forth at a very early age, whilst the females never have these fins developed ; the pectorals, on the other hand, are present in both sexes (although in the female in a less-developed state), but are always late in appearance. As compared with Latr. pellucidus, the difference in the exterior between the sexes in the present species appears in several ways already at a very early period, whilst this difference in Latr. pellucidus, as stated above, only becomes apparent in mature specimens. The construction of the body is thin and elongated, very compressed, and does not, as is the case in Latr. pellucidus, practically increase in plumpness in the spawning-season. In a full-grown specimen, ready for spawning, with a total length of 46 millims. (caudal included), the length of the head is about 10 millims, and is contained 4| times in the total length/ The greatest height (5| millims.) continues almost unaltered from the occiput to about a head's length from the caudal fin, and is contained 8J times in the total. The vent, on the posterior margin of which there is a small papilla, is situated halfway between the snout and the root of the caudal, and in some individuals projects in the form of a short tube. In the female, which, as stated above, is considerably smaller than the male, the head is somewhat more pointed. In a specimen with the eggs ripe the head is contained about 5 times or a little more in the total length. The diameter of the eye is one fourth of the length of the head. |