THE MAGAZINE

OF

NATURAL HISTORY.

MAY, 1829.

ART. I. On certain Effects produced by Fresh Water on some Marine Animals and Plants. Read to the Belfast Natural History Society, by the President, JAMES L. DRUMMOND, M.D., December 30. 1828.

DURING the past summer, a part of which I spent at the seaside, I was anxious to confirm, beyond a possibility of doubt, an observation which I had made several years ago, viz. that when the Squamous Sea Mouse (Aphrodita squamàta) is put into fresh water it dies almost instantaneously. I could not, however, obtain any specimens, but I am certain, at the same time, that it is a fact; for, on a former occasion, I brought from the shore seven or eight specimens of that animal alive in a phial of sea water, and I found in them all, that, although perfectly brisk and active in the sea water, the moment they were dropped into a basin of fresh water (and I made the trial on them one after another), they immediately sank to the bottom, and never again exhibited the slightest symptom of life or motion.

The observations I have made lately on another species of animal, of much larger dimensions, are not a little singular, and are, I apprehend, altogether new. I obtained a number of living specimens of the worm, which the fishermen call the White-worm, or Lurg, or Lurgan. It is the Nèreis cærùlea of Linnæus. These specimens were quite fresh, and were brought to me in a bowl of sea water. When handled, they moved with great vivacity, convoluting or twisting their bodies from side to side, like the larva of a gnat, or else swimming with great velocity round the basin. They were about as thick as one's little finger, and fully a foot in length.

On putting one of them into a basin containing some fresh water it sank to the bottom, and lay for a moment motionless, as if stunned. It then dashed here and there through the water, VOL. II. .No. 7.

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violently lashing its anterior and posterior ends from side to side: but this extreme agitation continued only a few seconds; when the animal subsided to the bottom, unable to exhibit any farther signs of motion than some partial convulsive twitches in different parts of its body, or a quivering here and there in its segments or articulations. The skin of the body was contracted in various places, so as to present a wrinkled or withered appearance. In six minutes from the immersion the animal seemed perfectly dead; the wrinkled appearance of the skin was gone, and not the slightest mark of irritability appeared in any part. The other specimens, eight in all, exhibited the same phenomena with little variance. None of them showed any appearance of vitality after ten minutes' immersion. Three of them protruded very slowly their remarkable ventricose proboscis (if the latter term can be at all appropriate) during their last expiring moments, and so it remained after death.

I allowed the above specimens to remain in water all night; and on the following morning, on going to put them in spirits in order to preserve them, I was surprised to find them so rotten, that they fell in pieces by their own weight, and were quite useless as specimens. They had not, however, acquired any offensive or putrid smell.

Some days afterwards I obtained a fresh supply of living specimens, some of which were entire; but a number of them were in fragments, having been cut through by the spade in digging. The latter were quite alive, and seemed to have suffered no more in point of vitality by having been cut, than the common earthworm does under similar circumstances. I had proof, too, that the being cut through does not prove fatal; for, in one of the entire specimens, about 2 in. of the tail end was a new production. The animal had, at some prior period been severed by the bait-digger, and a new portion had been restored. This portion, as is generally the case with reproductions, was smaller in diameter than the rest of the animal. It was also of a paler hue, and the line of demarcation between the old and the new parts was very distinctly marked.

The separate pieces of the cut worms, even those which wanted both head and tail, were affected by the fresh water in the same way as the entire specimens: they were first thrown into violent convulsions, then became affected with transient spasms, and, in a few minutes, all appearance of vitality was extinguished.

The first idea that struck me, as to the possible cause of these phenomena, was, that perhaps the water, from wanting the density of sea water, was unfit for respiration, and that there

fore the animals had died of suffocation. Pennant states that the torpedo dies in fresh water almost as soon as in the open air; but I had already ascertained that these worms will remain in air for many hours, without seeming to suffer any inconvenience.

I had a number of specimens lying on a plate motionless; for, unless disturbed, they are little inclined to move. I dipped my hand in fresh water, and with a jerk, sprinkled some drops of it over the plate, and the specimens on it. In about two seconds the worms were all in violent agitation, rolling round on the longitudinal axis of their bodies, and writhing together in apparent agonies. After a few minutes the agitation ceased, and they again lay motionless. I now tried the effect of touching an individual with a small drop of fresh water. The part to which the latter was applied, almost immediately contracted in the manner that a leech contracts at the place where a little salt is applied to it, and then, the whole animal became agitated and dashed violently about the plate, frequently, at the same time, protruding and contracting its proboscis. Similar effects followed every trial I made, and it mattered not what part of the animal was touched: the smallest drop of water from the point of a probe produced the partial contraction at the part, and then the general convulsive writhing and agitation of the whole body. Even fragments of the worm were similarly affected. It appeared to me, however, that the mouth extremity was more sensible to the touch of the poison than any other part, as the convulsive efforts which followed seemed more violent, and longer continued than when the water was applied elsewhere.

I made similar trials on many of these animals, and invariably found the same results. The most striking way of exemplifying the virulent effects of fresh water is, when the worm is at rest to apply consecutively from the point of a probe ten or a dozen small drops of sea water to any part of it, this causes no alteration; the animal continues motionless. If we then change the drop to be applied from salt to fresh, the very first application of the latter immediately produces the phenomena above described.

In whatever way it is that fresh water proves so poisonous and fatal to this species, one thing is obvious, that the animal can never propagate except under the influence of sea water. It can never colonise rivers or lakes, and the subject, if farther pursued by experiments on other species, may, perhaps, throw some light on the distribution of animals. The Lurg-worms cannot even safely inhabit those parts of the shore which are long uncovered by the sea; a heavy shower of rain during

ebb tide might destroy them; and it is only a casual circumstance that one of them is found in the usual place of digging for bait. They must be sought for at the verge of low-water mark, and they are only to be found in plenty, and of full growth, during the neap tides.

The common Lug (Lumbricus marinus) is, on the contrary, generally dug out of the sand at a considerable distance from low-tide mark, and where it is left dry for many hours. Showers of rain, therefore, we should suppose, can exercise no deleterious influence on it; and accordingly I found that some lug, which I kept immersed for several hours in fresh water, did not seem to be at all incommoded by it.

That fresh water has a considerable influence on the vitality of some marine plants is obvious from the following remarks. When we examine fresh specimens of Fucus punctatus, Conférva setacea, or U'lva dichotoma, we find that they possess a very considerable degree of rigidity, or firmness. Now, I have observed that these plants, after being immersed in fresh water for a short time, lose their firmness, and become perfectly flaccid. They also change their colour in a material degree especially the first two. These, when gathered fresh, are of a garnet-red colour; but, when immersed in fresh water, the tint soon turns to orange.

These, however, are not the only changes which take place. I had long ago remarked that when recent specimens of Fucus punctatus or Conférva setàcea are immersed in fresh water for a few seconds, and then taken from it, they give out a crackling or crepitating noise, like that made by fine salt when thrown into a fire. I had observed, too, that during the continuance of this crepitation, Conférva setacea (especially if in fruit) projected minute globules of water, or some fluid, to a distance of several inches. I last summer observed also a weak crackling noise in Ulva dichotoma under similar cir

cumstances.

Now, in all these, the crepitation, when it ceases, which is in a few seconds, may be renewed by again dipping it in the fresh water, and then removing it; but at each successive time the crackling is weaker, and it ceases altogether after a third or fourth immersion. If the specimen, also, have been in the water longer than a few minutes, the crackling is very weak, or not perceived at all. The cause of it in Conférva setàcea I have clearly ascertained, and it may be easily seen, with the help of a common pocket magnifier, or even by the naked eye.

I poured some fresh water on a common white plate to the depth of about one twelfth part of an inch, and in this I put a

portion of the plant quite fresh from the shore. It remained for several minutes quiescent, and then some of the divisions of the frond exhibited sudden startings like spasms. I had repeatedly before been amused by watching this appearance on a larger scale though with the naked eye, by putting a bunch of the plant in a basin of water. When so placed it soon assumes the appearance, to a considerable degree, of being animated; instantaneous startings are observed in the chief branches, along with lateral motions of the smaller branches, which are seen to move towards, or to diverge from, the former.

But the cause of these startings, and of the consequent motions of the branchlets, was more obvious, by observing what passed in a portion of the plant laid in a thin stratum of water on a plate, as above alluded to. The colour of the specimen was, when so placed, homogeneous throughout; but whenever the startings took place, a change began to take place also in the colour. The joints of the plant are filled with the coloured fluid; and while it is in the salt water the septa, or partitions between the joints, remain entire; but when the influence of the fresh water is felt, the septa burst, and the contents of one joint are exploded into the next, the colouring matter, at the same time, losing its uniform tint, and curdling into grains, or granular points of a dark hue, as if concentrating itself in order to part from the fluid through which it had been before uniformly diffused. From the violence with which the contained fluids are urged through the partitions of the joints, breaches form in the sides, also, of some of them, and then at every new spasm a quantity of the colouring matter is hurried through these lateral breaches into the circumambient water. The latter explosions present under a common magnifier an extremely interesting appearance. They are instantaneous; and when the projected fluid has attained its extreme distance, the colouring matter suddenly settles in a cloud of dark grains, so as to give not an unlively idea of a bomb-shell in the act of bursting. Repeated explosións take place from the same breach, but at very uncertain intervals. Sometimes several occur in rapid succession, and again half a minute or more intervenes between them. It appeared to me that each explosion from the lateral breaches was caused by a new rupture between some two joints.

These observations I repeated many times, and I here state what I remarked as exactly as is in my power. They are only, however, what I observed with a common magnifier, or with the naked eye; but, perhaps, a more patient research,