On the 8th of May, chancing to cross a small stream, I saw a number of Lampreys in the act of spawning, and remembering the queries of your correspondent, I stood to watch their motions.  After observing them for some time, I observed one twist its tail round another in such a manner, and they both stirred up the sand and small gravel from the bottom in such a way, as convinced me it was a conjunction of the sexes.  However, there were so many of them together, and they kept so continually moving about, that I could not single out the two individuals, and thus ascertain whether they were male and female; but I felt so desirous of being able to set this question at rest, that I went again next morning, and was fortunate enough to find only two, a male and a female.  I then witnessed several sexual conjunctions, during which the sand and small gravel was stirred up by them, and each of which was followed by the ejection of a jet of eggs from the female.  I then caught them both, and dissected them.  The sexual organ in the male was projected above a quarter of an inch, and the body filled with milt; the female, although she seemed to have shed a considerable quantity of her spawn, had still a tolerable stock remaining.

I frequently afterwards witnessed the same thing, and always found the same difference of sexes; in fact, there was generally no difficulty in distinguishing the male from the female, without taking them out of the water:  the latter might be readily known by the enlargement of her body, and the former by a still more incontestable token.  I have been induced to describe this more minutely than I otherwise should have done, in consequence of the mystery in which the propagation of fish has been wrapped hitherto; and I am not aware that what I have described has been witnessed by anyone before—­at least I don’t know that it has been recorded.

I caught half-a-dozen Lampreys, four males and two females, and preserved them in spirits, and these I now forward to you.

I am unable to give the same information concerning the large Lamprey, having never seen it in the act of spawning; but I have repeatedly caught both milters and spawners of species with the milt and roe as distinctly visible in them as it is in the Salmon or any other fish.

I am of opinion that the P. marinus and the P. fluviatilis are distinct species, for the following reasons:—­1st.  Because the latter stays with us the whole year, while the former only ascends the rivers to spawn, and then returns to the sea immediately. 2nd.  Because fish that are in the habit of descending to the sea, never (unless the small Lamprey be an exception to the general rule) arrive at maturity [13] until they have visited it; and, 3rdly, because there are no intermediate sizes (at least in the Ribble) between the one which, although only six or seven inches long, and an ounce in weight, is yet capable of propagation, and the one of a pound.  Not having one of the larger kind to refer to, I am unable to point out any specific difference of form. (May 2nd, 1832.)