Abbildungen der Seite


completely opposite inference from the curer, who published a Natural His. same premises. Suppose, for instance, tory of the Salmon in 1830, is attacked (and I state the incident as it was re- in the same manner; and his statelated in the Courant newspaper, a few ments, founded on experience, are years ago), a large trout to be caught treated with disrespect, and as not to in the Canal, in a nearly exhausted be believed, because he counted only state, with a frog mounted upon its 54 vertebræ in the backbone of the back, and that the said trout was in- salmon, when, according to Dr Knox, jured in the neck, opposite the frog's there are really 61. mouth,-might not the learned doctor, the Doctor, “an experience of forty like the narrator of the circumstance or fifty years as a salmon-curer and in the newspaper, very naturally sup

catcher has not enabled him to count pose that the frog was in the act of the backbones correctly.”—(P. 501.) devouring the trout? And, supposing And again, because Mr Fraser has the breed of frogs to be of national im- omitted to mention the “ internal paportance, and their food a grave mat- rasitical animals," " I confess," says ter of philosophical enquiry, would Dr Knox, “ this excites strong doubts not this fact be considered as incon- in my mind as to the accuracy of Mr testable proof of the nature of their Fraser's observations generally, and aliment, however different from the causes me to undervalue altogether his frog's habits, and direct evidence that forty years' experience as a salmon. the reptile had taken at least one curer.”—(P. 502.) And again, “ Mr mouthful? The fact of the frog on the Fraser has a mind capable of rising back of the trout, and clasping it with above all prejudices in the support of its arms, is of undoubted occurrence truth."-(P. 502.) the reason assigned is mere matter of Now, it to be able to count the opinion, and in this case would be per- number of vertebræ in the backbone of fectly erroneous. To those acquainted a salmon correctly be the rule of judgwith the natural history of the frog the ing of the credibility of testimony in solution is apparent, without invol other matters, what shall be said of Dr ving the crime of trout-murder. At Knox, if his enumeration be not itself the usual period of the year, the in- correct ? Mr Yarrell, whosc knowstinct of reproduction in these animals ledge of fishes, internally as well as exis strong, and, failing females of their ternally, requires no praise of mine, own class, the male frog frequently makes the number of vertebræ in the sits the usual time upon the back of a salmon sixty! and so does the Rev. fish. (See Blumenbach and Spallan- Mr Jenyns, in his accurate work on zani.) I have heard of ponds in Eng. the British Vertebrate Animals. “Acland being nearly cleared of trout cording to Dr Richardson” (says Mir from this cause, where frogs abounded; Yarrell), “the cæcal appendages are the trout being literally ridden to in number from 63 to 68 ; and several death by these amphibious equestrians. observers have stated the number of Now, the natural conclusion of one vertebræ to be sixty, which I have ignorant of the habits of the animal, repeatedly found to be correct.”— on such an occurrence coming under British Fishes, ii. 6. his notice, would be that the frogs had But Mr Fraser, it seems, has given seized upon the trouts for the pur- other and greater offence in speaking pose of devouring them ; and one of the salmon's food.

In respect to more imaginative might naturally the food of the salmon” (says Dr enough conclude that imps in the Knox), “Mr Fraser has notions also shape of frogs were running sweep- perfectly local; that is,confined to himstakes in a submerged racing-course. se!f. And as the whole passage adIt need not be said how far from truth mits of no sort of analysis, and as, inthese inferences would be; but such is deed, no person having the smallest the mode in which the author of the knowledge of natural objects would paper before us treats the evidence think it necessary to read the article given by professional fishers, and twice, much less to examine it seriousothers, before a Committee of Parlia- ly, we shall simply quote his own ment. If they err in opinion, their words, and then leave it :-" Their evidence as to facts coming under their digestion is so quick, that in a few express cognisance is not to be be- hours not a bone is to be discovered. lieved.

Of this I have had various proofs, in Mr Alexander Fraser, a salmon- trouts caught by a par as a bait in set lines. Fire or water could not con- the ova of fishes to the action of the sume them quicker.'”—(P. 501.) Sir gastric fluid. But beyond this single Humphry Davy shares in the con- remark, that ova of the Asterias glatemptuous reprehension implied in the cialis is found occasionally in the stointroduction to this paragraph; for he mach of the salmon when in season, says, " their digestion appears to be there is nothing in the memoir that very quick"-(Salmonia, p. 130); and can be said to have extended our other writers corroborate the obser- knowledge of the food or natural hisvation.

tory and habits of the salmon. As to the food of the salmon, then, it appears clearly that this food, both The next portion of Dr Knox's pain rivers and in the sea, was well per which claims notice is “ the Geneknown, and recorded by almost all ration of the Salmon, the Growth and writers on the natural bistory of fishes, Progress of the Smolt, and the descent long before the observations of Dr of the kelt or spawned fish to the Knox appeared. That food is, gene. ocean,"-(P. 471); and here again rally speaking, worms, insects, and the author seems to labour under a small fishes ; the first term including lamentable ignorance of what has been the Echinodermata of modern writers, recorded on this subject before the and the second the modern class Crus- appearance of his paper; for he detacea. The author's criticism on Dr clares he knows « of no continued Fleming saying that salmon go “into series of observations on the subject, estuaries in search of worms and other published by any one, of an authentic bait," is almost unworthy of notice. nature, and so as to admit of no doubt.'' Worms may mean only earth-worms To fill up this chasm, he resolves to in the vocabulary of Dr Knox, though detail the history of the salmon smolt, the use of the word in the plural num- from its first deposition under gravel, ber might have suggested to a person in the form of an egg, to its ultimate so learned, that there might be marine- disappearance from the fresh water worms as well as earth-worms in the streams; “remarking, that everything estuary alluded to. But in point of stated therein fell under my own imfact, one of the stomachs now on the mediate personal observation.” The table, confirms even the verbal accu

dates of observation are - Nov. 2 racy of Dr Fleming, had he even (1832 ?), Feb. 25, March 23, April 1 meant, as is sneeringly imputed to him, and 19, and May 5 (1833 ?). The merely earth-wormsfor there is ac- results of these observations will be taally an earth-worm in that stomach, stated in the sequel of this notice, as washed down probably from the banks compared with the prior observations of the river by the receding tide. The of others. It may now, however, be evidence of practical fishermen and mentioned generally, that Dr Knox others fully establishes, what previous has not stated a single fact regarding writers had asserted, that small fishes, the deposition or growth of the ova of particularly sand-eels and shrimps, the salmon—the periods of their asform a chief portion of the food of the cending the rivers where they breed, salmon, without, however, excluding and their return again to the sea,uorms, and other animals found on which had not been observed and rethe shores which salmon frequent. corded with much greater minuteners That they may also feed on the ova of prior to the publication of his paper. the Asterias glacialis ; on the ova of Salmon ascend the British rivers at fishes; and even, like the haddock, different periods according to the seaswallow this and other species of As- sons, generally from September to terias entire, I have no reason to January, and deposit their spawn durdoubt, and would willingly admit, ing the months of November, Decemeven on less than the single evidence ber, and January. This is fully ascerof Dr Knox, because that class of tained by the evidence led before the animals is, amongst others, stated by Committee of the House of Comall authors to form the food of the sal.

The names of the witnesses mon. And the existence of ova in the need not be here mentioned ; but they intestinal canal or stomach of the sal- state the period of salmon ascending mon and herring, when the other por- the rivers on observations for periods tions of the food are decomposed, is varying from a few years up to no less easily accounted for, from the known than forty. This evidence was taken resistance of the coriaceous envelope of in 1824-25. Dr Knox, in the single



instance he mentions, says, that a pair and over all the rivers of the emof salmon were observed in the Whit- pire. tader, one of the tributaries of the The mode in which the salmon deTweed, to be spawning on Nov. 2. posit their ova in the gravelly bottom

The ova remains in the spawning- of shallow streams, is minutely describbed or gravel for three or four months, ed by Mr George Little (Report, p. according to Dr Fleming ; according 108-9), and, indeed, has been known to Mr John Johnstone, from the ova for centuries ; for John Monipennie deposited in November, December, has so long ago graphically recorded and January, the young rise from the the manner in which this instinctive gravel in March, April, and May ; work is done. “ In harvest,” says he, according to Mr John Halliday, the “ they come from the seas up in small spawn deposited in November, De- rivers, where the waters are most cember, and the beginning of January, shallow, and there the male and feis disengaged from the spawning-beds male, rubbing their bellies or wombs from Joth March to 10th April ; so one against the other, they shed their that it appears, on an average of sea- spawne, which forth with they cover sons, the salmon roe lies about four with sand and gravel, and so depart months, or 120 days, in the gravel beds away.”—P. 195. before the young appear. But accord- As to the developement of the ova ing to Dr Knox, in his single observa- under Dr Knox's “ own immediate tion of the Whittader pair of salmon, personal observation," — though the the ova took 142 days “to become ova would not, it appears, bear transfishes somewhat less than an inch in mission to Edinburgh-it really se length," but still "embedded in the

unnecessary to notice such an evidentgravel."-(P. 473.) On the 19th of ly imperfect experiment, particularly April the fry are "eight and even since a very full and interesting ac. nine inches long;" and on the 2d May count of the gradual developement of they still abound in the tributary the ova of the salmon, accompanied by streams, but are not so numerous as an accurate engraving, is given in the before, they are not increased in size, evidence of a gentleman before the and are, in all probability, the fry of Parliamentary committee. To that a later deposit.”—(P. 473.). So that engraving, and the description of the amount of Dr Knox's information the report in general, I beg to refer here is, that the spawn of a single pair any one who takes an interest in the was hatched in April, and other fami- subject. At the same time it is proper lies of other fishes were of a later de to mention, that there is an interesting posit, and appeared in May. The article on the “ Spawn of Salmon, witnesses examined before the Com- by Mr Schonberg, printed in Sir mittee of the House of Commons had David Brewster's Journal of Science stated all this much more fully in 1824 in 1826, accompanied also by an enand 1825. Thus, Sir Henry Fane says graving of the ova in different stages the fry descend in April and May- of growth. Both these sets of figures, Alexander Fraser, early in April and and the accompanying details, corresMay– Rev. Dr Fleming, March, April, pond with one another in every essenand May– Mr George Hogarth, jun., tial particular ; but

oth at the same April and May-Mr William Stephen, time differ widely from the details March and April, to 14th May, ac- given by Dr Knox. Neither does the cording to the temperature of the sea- Doctor even hint in his paper at the son and the situation of the different existence of such details or figures, rivers. It appears, therefore, that Dr though he could scarcely be ignorant Knox's single observation is corrobo- of what is stated in the Report, which, rative of the evidence led before the he asserts, he had repeatedly read over. Committee, as far as a single instance To pass over discrepancies which in a single river can; only it is to be materially lessen the value of his reobserved, that he makes his single ob- marks, Dr Knox asserts, that “ servation, made he says by himself, taken from the bed of a river at any the rule for spawning in all rivers by time from January to March inclu. all salmon, without reference to sea- sive, and not sbaken or carried far, son or situation ; while the evidence will live and become developed, i. e. of practical men give the average re- grow to fish of about an inch in length sult of many years of observation, ex- in a small glass full of water, changed tended over every variety of season, not oftener than once a week,” p. 476.


Then follows a passage in which tity of trout in rivers or lakes." temperature is said to have some effect (Salmonia, p. 82). “ In all experiin hastening or retarding the deve- ments of this kind" (continues Sir lopement of the ova, though in his Humphry) “ the great principle is, reckoning by days such agency is to have a constant current of fresh and necessarily excluded ; and he adds, aërated water running over the eggs. that " after having cast the slough, The uniform supply of air to the fætus they will live about ten days (seldom in the egg is essential to life and or never longer) in water unchanged, growth ; and such eggs as are not apparently thriving, growing, and supplied with water saturated with darkening in colour (if exposed to the air are unproductive."-Salmonia, light) every day.”—P. 477.

p. 82, 83. This assertion, of the ova and This necessary aëration, and exsalmon fry living a week and even ten posure to the influence of the sun's days in a small glass of unchanged rays, explains at once why salmon water (almost the only original obser- seek the gravelly bottom of shallow vation in the paper) is in complete streams for the purpose of spawning ; contradiction to all experiments that and the same instinctive impulse which have been made on the developement guides the salmon, induces the herring of the ova of this genus of fishes. and the cod, among numerous other " It is said by Sir H. Davy” (says Dr fishes, to approach banks and shores, Knox), “on the authority of a person of and thus carry boundless provision to the name of Jacobi, whose writings countless animals. It was a curious I have not met with, that the ova of circumstance in Jacobi's experiments, salmon are deposited in the gravel of that the effect of his impregnation of rivers under streams, in order that the ova with the milt, often produced they may be perfectly aërated, or ex- in the trout monsters with two heads, posed to water which is so. This &c.—so different are the rude attempts reason, which appears so plausible, is of man from the instinctive workings probably not the true one." -(P.476). of nature. The person of the name of Jacobi here The experiments on the salmon ova mentioned, though unknown to Dr by Mr Hogarth and Mr Schonberg, Knox by his writings, was a Counsel- who both traced their developement, lor of State to the King of Prussia, and from the first appearance of life, till a well-known experimenter on the the animal was an inch in length, artificial fecundation of the ova of further demonstrate the necessity of fishes. His experiments appeared in this aëration. With “frequent changes the Berlin Transactions for 1765, and of water, Mr Hogarth succeeded in have been referred to with approba- hatching the ova, and by changtion by almost every writer on the ing the water frequently' the ani. subject of fishes since. These expe- mals appeared vigorous for three riments were made chiefly upon the weeks, after which they became restova of the genus Salmo; and he found less and uneasy.' (P.92). Mr Hogarth that by expressing the unimpregnated also tried one of the fry hatched in ova in water, and afterwards applying fresh water, if it would live in salt the milt, the ova became impregnated, water; but found that it immediately and went through the usual develope- showed symptoms of uneasiness, and ment. In making these experiments, died in a few hours.'” (P. 92). The one thing essential to their success figures of the ova, and the young aniwas found to be necessary, and this mal in its different states, were drawn Was the frequent, almost incessant, by an artist, at the request of Mr changing of the water; and hence he Hogarth, and an engraving of them is justly concluded, that the aëration of appended to the Report of the Comthe water where ova are deposited, is mittee on the Salmon Fisheries, necessary to the developement of the Mr Schonberg found the frequent ova. Sir Humphry Davy, notwith- change of water equally indispensable. standing Dr Knox's gratuitous as- “ Changing of the water" (says he), sumption of his incompetency to make “and if possible from the same river, observations on the generation of the must be repeated hourly, and they salmon, “ had this experiment tried must likewise be exposed to the sun's twice, and with perfect success ; and influence.” (Journal of Science, v. it offers" (he adds) “a very good mode 238). The developement of the ova of increasing to any extent the quan- is well represented in the engraving which accompanies Mr Schonberg's whether we have an early spring or valuable paper.

The details of his rot; sometimes there may be two or experiments are more extended than three weeks of difference, according to those of Mr Hogarth ; but both agree the season.' “ I have observed, when in all the more important points. we have early warm weatlier, the fry

Dr Knox's experiment, although come early, and when we have a late said to have been made under his own spring, it is later before the fry rise eye, is contradictory of the fact that from the gravel bed." (P. 109). aëration of the water is necessary, as

The descent of the fry to the ocean he, or the person who took charge for is, in the Avon, according to Sir Henry him, appears to have kept the fry in Fane, in April and May-in the water unchanged. But better evi- Ness, according to Alexander Fraser, dence than this will require to be pro- early in April and May-in the Don, duced before we can give up the March and April, to the middle of hourly and daily observations, bearing May-in the Dee, April and Mayall the marks of truth, made by Mr in the Tay, March, April, and May; Hogarth and Mr Schonberg, in oppo- and so on, according to the season. sition to the statements and examina- The kelts, or spawned fish, descend tions of Dr Knox or his assistants. Of with the winter and spring floods. But Dr Knox's candour and fairness in not the dates given in evidence by the referring to the experiments of those numerous and respectable witnesses gentlemen, though one of the ap- examined before the committee are peared in the Parliamentary Report not be taken as absolute periods, which he so much abuses, and the common to every year. The tempeother in a Journal consulted by every rature of the season must be a powerone with any pretensions to science, I ful element in determining the ascent leave others to draw the inferences of the salmon, the deposition of the limiting myself to the plain statement ova, and the hatching of the ova; in of facts. Of course I hold, with all fact, the temperature and other cir. writers on the subject, except the cumstances, there is every reason to author of this memoir, that the aëra- believe, might have the effect of hastention of the ova by the frequent change ing or delaying the process of repro. of water is necessary to the develope- duction, as the same meteorological ment of the salmon fry in rivers ; and agents are known to hasten or retard that this, and a certain exposure to the annual harvest, or prematurely the rays of the sun, influence the ap. bring out or delay the appearance of proach of fishes to the banks and shores many of the insect tribes. With the upon which they deposit their spawn. exception of Dr Knox fixing a deter

In reference to Jacobi's experi. minate period for the developement of ments, the stucking of ponds or lakes the ova in the gravel till the appearwith any desired species of fresh-water ance of the smolt, I say, with this exfishes, is, by these experiments, proved ception alone, any reader of his paper, to be comparatively easy ; for he and the minutes of evidence, might found that the ova could be impreg. have naturally enough supposed, that, nated, and the animals from these with regard to these points, he took ova hatched, after the parent fishes his information from the Parliamenthad been dead four days. Even the ary Report, which he reprobates, and Vendace of Lochmaben might thus be from the testimony of witnesses whom introduced into other lakes without he declares unworthy of all belief; much danger of failure, by catching a and the strong coincidence between few of these fishes previous to spawn. the Doctor's periods of migration as ing. It is well known that the Chi- related in the Transactions, and what nese stock ponds with impregnated was stated by these gentlemen six spawn of fishes.

years before, must either appear very The period of the salmon fry rising strange, or the witnesses have not defrom their gravelly bed has been served that unmannerly abuse which already stated generally as occurring has been dealt out to them under the in March, April, and part of May; sanction of the Royal Society of Edinbut this of course depends upon the burgh.

Mr George Little gives de- Another particular noticed by Dr cided evidence as to this point. " A Knox in his observations upon the great deal" (says he) “ depends upon salmon smolts is, that they will not the season at the time of the year, “ bear the slightest handling-they


« ZurückWeiter »