The author has been induced, he states, to make inquiry on this subject, in consequence of a recent averment, founded on a reported experiment, that the ova of the trout taken from the abdomen of the parent fish, and not afterwards mixed with the milt, have proved prolific.

He first gives an account of many trials made to test the accuracy of the conclusion that the ova of the Salmonidæ may be impregnated ab externo, the results of all which have been negative, and remarkably contrasted with those in which, after exclusion, the milt and roe have been mixed,—impregnation having been effected and the eggs rendered prolific.