These observations are given in seven sections:—

In the 1st, the author treats of the air-bladder of these fish, and the contained air, which he found, in every instance that he examined it, to be chiefly azote.

In the 2d, he points out a mistake he had fallen into in the instance of the female fish, as regards its abdominal aperture, which, in a former paper he had described as open only for the passage of the ova; on further examination made on the larger species, he has ascertained, that though virtually closed, except during the spawning time, it is not absolutely, either by a membrane or adhesion.