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The most incredible superstitions existed in earlier generations with reference to the origin of eels. Aristotle himself taught the spontaneous generation of the species, and Pliny imagined that a fragment of skin severed from the parent fish was capable of reproduction. One learned philosopher laid down a splendid rule for perpetuating the breed. Take, said he, a couple of freshly-cut turfs which have been exposed to the fresh dew. Lay these face to face in the open air, and within a few days will be found a number of vivacious eels therein. A tradition existed in England that the young fish developed from a fine thread of black hair plucked from the tail of a mare. In parts of Germany the parasitic internal worm of a blenny or similar small fish has been thought to produce eels, and in Sicily to this day they are believed to be derived from a shellmollusc. Even in the present century learned naturalists have declared the eel to be hermaphrodite, the sexes not having been distinguished until the present generation. All the eels captured in rivers were found to be reproductive in themselves. On certain long ribbons of fat, at the upper part of the intestine, the minute ova were long ago demonstrated to exist; but no male organs could be discovered, nor was there any trace of a special duct for the expulsion of the eggs. The fish might be ovo-viviparous, it was thought, or deposit the ova in the usual manner. But where was the male to shed milt over the eggs? Apparently they did not exist in the waters.

It was not until 1873, Dr. Day remarks, that Syrski, of Trieste, reported the discovery of the male organs in a river eel, which was found to be slightly smaller than the average-sized female fish. Under the microscope he also saw the vivified spermatozoa ejected by the male eel. Through his experiments at a marine biological station on the Adriatic it was clearly proved that the sexes were perfectly distinct. Further investigation has also shown that the male eels keep almost entirely to the salt estuaries, rarely ascending the rivers; hence they are seldom seen. The females migrate each year, returning in due course to the sea in anticipation of the breeding season. The young elvers, as we have seen, advance to inland waters in March. No one has seen the ova deposited, and a link yet remains undiscovered. A writer in Longman's Magazine very lately gave some interesting details with regard to very minute eels seen by him in the mud of the Bristol Avon-of such infinitesimal size, in fact, that it required a microscope to examine the washings of the mud; but it places the matter beyond a doubt that the actual breeding occurs in the Severn tidal way. Yet it has not been distinctly shown that elvers are produced alive; the fertilised egg,

detached from the parent body, has still to be obtained as it is certain to be if existent. The probability is, that the ova are discharged into the mud, to be impregnated by the male fish and hatched in situ, after expulsion. Being actually born in the mud, it would account for the dexterity shown by the elvers in gliding through their native element; it is the acquired habit of countless generations of eels. Great conger eels are now and then taken in the salmon baskets or putchers in the lower Severn. It is an erroneously-held opinion amongst many of the fishermen that they interbreed with the fresh-water eel; needless to state, this is completely false: there is little affinity between the sea and river species or genera. I once caught a huge fresh-water eel in a net from a pier that had evidently lived for several years in the salt water. The colour was a beautiful rosy-pink-almost as bright as the hues of a red mullet-and the weight was 5 lbs. The shape of the head and mouth was altogether different from that of a conger; it was admittedly a river fish changed in colour through the action of the salt water.

Most of the authorities on British fishes agree that eels frequenting rivers-and even ponds-only breed in salt water; but there is still some obscurity concerning the question. We know what indomitable perseverance is exhibited by these fish in seeking the fresh water; and few people-if any-have, I imagine, seen small elvers in an absolutely isolated pond. In the first place, very few ponds exist without a connection, either by drains or springs, with other water: nor, if such can be found, are they beyond the influence of floods; or, again, they are near enough to streams for the eels to crawl overland through the herbage to the desired goal. On the other hand, there are those who truly urge that ponds do exist, far away from a possible water connection, where eels have thriven from time immemorial, increasing in number without replenishment or importation of their kind.

Less than a year ago I found an isolated pond, attached to an old farmhouse which had once been a monastery. The stagnant water was enclosed by walls; it abounded with fat eels, and I thought to myself-this is a fair example of eels breeding in a pond. When a more complete examination, however, came to be made, I was astonished to find one pike in the same enclosed water. Those living in the immediate vicinity informed me that in the spring the Severn floods not unfrequently rise to the very walls of the building, and, finding an ingress through a doorway, rush into the garden and house. In this way the pike must have entered the pond, and the supply of eels must have been replenished from time to time. So it has been in every case; I have never yet discovered a pond containing eels that had absolutely no connection at some time or another with running waters. This fact I have observed that in tarns or small lakes high up in the mountains eels are never found.

Yet I do not myself feel convinced that eels never breed in fresh water, although proof of such a thing has never come under my notice. The two fairly marked species may, indeed, have different habits, the one necessarily seeking the sea, where the males always remain, and the other having sexual intercourse in ponds or rivers. With this contingency in view it might be well for local naturalists to follow out the investigation where eels are known to exist in isolated ponds. First of all the male and female fish must be distinguished; then the ova must be discovered also by dissection; and then, if possible, the various stages of the ova and immature elvers require to be seen in the mud of the pond. Failing the production of a complete chain of evidence, it must be assumed that the fresh-water eels all propagate seawards, as they have been shown to do in the Avon mud near Bristol.

Shortly after the elvers have passed up the Severn there is a migration of fair-sized eels from the sea. At Framilode, near to Gloucester, they have been actually heard when the water is at the lowest ebb. At night, directly the tide commences to flow, the eels emerge from the mud in great numbers. A peculiar sound emanates from the movements of the fish-a kind of suction, possibly produced by the frequent opening and closing of the mouth, which is distinctly audible above the trickle of the eddying stream. At such times the old-fashioned mode of "bobbing for eels" is wonderfully efficacious. A number of worms are tied together at the extremity of a loaded line. The eels, sucking freely at so tempting a morsel, can be drawn up into a bucket floating by your side or held in readiness to receive the slightly attached fish; as there is no hook to secure them, each one drops off as the body leaves the water, and the receptacle must necessarily be close at hand. Like many esteemed delicacies of the table, eels are foul-feeders, revelling in offal or anything that partakes of the nature of putrescence. The sentiments of "the Lady Jane" were founded on faithful observation: eels would assuredly fatten in a pond that contained a dead body. As the shrimps, prawns, and lobsters are the scavengers of the sea, so the eels perform a similar office in the rivers.

Hitherto I have dealt principally with the upward spring migration of eels, but there is a well-defined downward movement during the autumn months, the exact time being governed, as in the spring, by

the temperature of the water, the direction of the wind, and the height of the river and its tributaries. In the Severn, I believe, this downward migration usually takes place in November. When heavy banks of wreathing mists rise from the damp meadows, or hams, by the waterside, and after the autumn colchicum has shed its mauvecoloured bloom, the eels begin to move towards the sea-where the male fish await their arrival. Doubtless the eels are the survivors of previous myriads of ascending elvers-those, in fact, which escape the attacks of predacious enemies, or capture at the hands of eager fishermen. One might think that a proportion of male fishes must be included in the descending shoals; but they have yet to be detected. Perhaps they die in the immature stages owing to unsuitable surroundings. Certain it is that if all the hosts that penetrate the inland waters came to maturity other aquatic life would be crowded out of existence. The equilibrium of nature demands the extermination of elver swarms each year in order to restore the balance of life; possibly some of the larger fishes prey on young eel-kind.

During the downward course great quantities of eels are taken at the mills and weirs in traps or putchers judiciously baited with offal or some congenial and alluring food. Almost every fish-if not every one that has been examined by an expert who can dissect the body, has been found to be a female fish, although the fact is not at this time so easily established as in the estuaries in spring time, when the minute egg-cells are developed in the ribbon-shaped frills of fat lining the upper portion of the abdomen. The water is now cold, and the eels are not seen near to the surface, preferring to swim deep down in the river. In the summer the head is not unfrequently seen above the surface of the stream, with the mouth slightly extended, apparently seeking insect food from above. Under these conditions I have seen an eel swallow an artificial trout-fly placed gently over its expanded mouth. If there are wooden piles, or lock-gates overgrown with confused weed, the eels will also in the warm weather suck diligently around the surface of the wood, feeding, I suppose, on the slimy substances thereon. Few fishes are more sensitive to electricity. At the approach of a thunderstorm, the erratic course of the highly irritated eels can be distinctly traced in still waters, as they dart hither and thither in excentric curves, manifestly influenced by the electrical conditions of the atmosphere. They will never take a worm at this time-like the trout under similar circumstances, which usually fail to rise or take a fly.

In conclusion, I do not consider that it is clearly proved that all eels go down to the sea; there is a contingent possibility that

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some deposit the ova, or breed entirely, in fresh water. possibility is, perhaps, remote; if it were the case, the males should be found in the rivers or ponds. Nor is the exact mode of production yet clear. In the mud of the Avon it is only the microscopic eels that have been found; the ovum, after its discharge from the parent body, has still to be detected. For the present, therefore, the life-history has not been entirely worked out. Dr. Günther (vide the introduction to "British Fishes") states that their mode of propagation is still unknown, but adds that they do not spawn in fresh water, and that they breed most likely but once during life. The proportion of males to females, he says, decreases according to the distance from the sea. Dr. Day, in discussing the life history of the river eel ("British Fishes"), gives but meagre details with reference to the exact mode of reproduction. He does not affirm that they cannot reproduce their kind in fresh water, or even state that the ova are deposited in the mud before they are hatched.

The fact that some cold-blooded animals reproduce their kind alive is shown, not only by several viviparous lizards, but also by at least one fish-the viviparous blenny. Sometimes the young of this animal emerge from the parent body four inches in length, the size apparently varying in proportion to the size of the mother. Conversely, there are at least two mammals, the duck-billed platypus and the echidna, which lay eggs; and there are birds in Australia which refuse to incubate their own eggs, leaving the operation to the action of the sun on the warm sands. Believing myself that the ovum of the eels is deposited in the estuarine mud, to be therein fertilised and matured, I should like to see the point more clearly demonstrated by competent observers. It is not a little strange that with regard to so common a fish-prevalent in all waters, and in all parts of the world-the precise observations should be wanting in a generation when Argus-eyed inquirers are penetrating in every direction, thirsting for more extended biological knowledge.

PARKINSON.

VOL. CCLXX. NO. 1921.

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