On the food of certain gregarious fishes / by R. Knox.

  • Knox, Robert, 1791-1862.
Date:
[1855]
Catalogue details

Licence: Public Domain Mark

Credit: On the food of certain gregarious fishes / by R. Knox. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    Lateral line precisely mesial in the Castle Loch vendace, but one-eighth nearer the dorsal line than the abdominal line in the Mill Loch. A section shows both these specimens to be female, with the ovary more fully developed in the Mill Loch vendace; the liver is evidently larger in the vendace of the Mill Loch : these differences, however, will not account for the great additional weight of 4 drs., and which evi- dently arises from the greater depth and thickness of the Mill Loch vendace. This greater depth and thickness of the body, and the larger head, seems to me to constitute the only specific differences between these two fishes. The difference in colour is very striking; but this seem to me to depend on the greater number of minute black spots of the rete mucosum in the Mill Loch vendace: the dark shade is so strong on the head as to obscure almost, if not entirely, the brain ; and thus the peculiar and much-dwelt-on heart appearance observed in the Castle Loch vendace is not seen in that of the Mill Loch. The scalesj which I took from the lateral line and near it, of both specimens pre- sent precisely the same appearance when placed under the microscope : I counted 30 rays on that part of the scale, in both specimens, which is exposed: the number of rings on the part concealed by the super- imposed scale is greatly more. The largest vendace I have ever seen was 9 inches in length. Another delusion in respect of the vendace was the supposition that the males lived apart from the females in deeper water, and hence be- yond the reach of the net. Like everything else in the history of the fish this also seemed a delusion ; for the net being drawn in the Castle Loch of Lochmaben, and near the castle, in presence of Mr, Murray and myself, of fifteen vendace which I examined nine were females and six males: this was in October, Nevertheless,! feel disposed to think that the males are not so numerous as the females, for of forty taken in the Mill Loch at one time only two were males. The males are lighter coloured than the females. (Thus terminated a popular delusion which had no doubt maintained its ground for centuries. The discovery of the food of the vendace, and of countless millions of other fishes to be spoken of immediately, was a gift of the microscope to science: it illustrates and perhaps.ex- plains many obscure points in the natural history of such fishes, and may one day lead to important results.—^c/t^erf io ihe original MSS. April 20, \S55.)