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Show 134 PROF. HUXLEY ON THE OVIDUCTS OF OSMERUS. [Mar. 20, As might be expected, I have found Rathke's statements, so far as the matters of fact are concerned, perfectly accurate. Between the latter part of January and the beginning of March of this year I have examined a number of female Smelts, and always with the same results. I may remark that the ovaries were fully developed in the former month, and that, in the first week of March, four Smelts which I obtained in very fresh condition were all females, full of detached ova and ready to spawn. Tbe abdominal cavity of a female Smelt, in this state, is distended by a mass of ova, which are closely compacted and coherent, but become readily detached from one another when the mass is gently agitated in water or other fluid. When the abdominal wall of the fish is carefully slit open along the ventral median line, the mass of impacted ova has almost the appearance of a vast single ovary ; and, indeed, Bloch appears to have been misled by this appearance (Rathke, I. c. p. 132). But it may be readily broken up and washed away ; and the two ovaries are then seen, one on each side of the middle line-not opposite one another, however, but the left in the anterior, and the right in the posterior half of tbe abdominal cavity ' (fig. 1, p. 135). Each ovary has the form of a half-oval plate, with the curved edge ventral and the straight edge dorsal. The latter is suspended by a narrow mesoarial fold of peritoneum from that pint of the dorsal wall of the abdominal cavity which corresponds with tbe ventral face of the air-bladder. The line of attachment of the mesoarium is parallel with that of the mesentery and a little distance from it. What may be termed the body of the ovary2 is a broad and thin plate, and its inner face is covered by peritoneum. The ovarian artery enters the left ovary at its anterior internal angle, and then passes backwards along the middle of its inner face, giving off branches as it goes. The artery of the right ovary runs from behind along its dorsal edge, and then passes obliquely across its inner face forwards. The outer face of the body of the ovary gives rise to a great number of ovigerous lamella of a broadly triangular form, which are disposed transversely to the length of the organ aud perpendicularly to its body (fig. 1, B, C). In fish which are not ready to spawn, these ovigerous lamellse are very thick, from the number of close-set ovisacs with which they are laden, and the clefts which separate them are extremely irregular. In those in which the abdominal cavity is full of eggs, the lamellae from which the eggs have been discharged remain as thin plates separated by tolerably regular interspaces as wide as, or wider than, the thickness of each plate. The outer face of the ovary is not wholly occupied by the ovigerous lamellse. On the contrary, the peritoneal layer of the inner face is continued over the ventral edge of the ovary, and ends at about a third or a fourth of the height of the outer face by a well-defined margin. Hence the outer face of the ovary appears transversely laminated only above and in tbe J Conf. Eathke, I. c. p. 135. 2 Conf. Eathke, I, c. pp. 121 & 175. |
