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 13, 1863.] much disputed in reference to the natural history of the crab. The young crab in its earlier stages was gravely described by various naturalists as a distinct animal. Naturalists are so ignorant of how the work of growth is carried on in the fish world—in fact, it is so difficult to investigate points of natural history in the depths of the sea—that we cannot wonder at less being known about marine animals than about any other class of living things. Pisciculture has settled the parr controversy, and to the system of artificial cultivation we must look ultimately for the solution of others of our fish mysteries. As to the crab dispute, it is only of late years that the various metamorphoses undergone by that popular crustacean have come to be understood. The crab yields a great number of eggs, and these, when hatched, yield an animal not in the remotest degree like the parent; hence the mistakes which have been so frequently made about the time necessary to mature a crab for table purposes. It was Slabber, a Dutch naturalist, who first started the idea of this crustacean metamorphosis; and, as in the case of Shaw and the parr, he was taunted with having made a blunder. He kept a zoea in water, in order that it might grow into one of the higher crustacea under his own eye; and so it was said that “Slabber lost his zoea in changing the sea water, and that another animal came with the added portion.” It was thought by all scientific men to be a wonderful discovery when Mr. Vaughan Thompson announced, in corroboration of Slabber, the remarkable fact of the genus zoea, founded by Box, being nothing else but the higher crustacea, in an early stage of their development. We know the kind of worms that our butterflies grow from, and most people are convinced that these crawling animals do get themselves changed into winged insects, and flutter out a brief life in the sunbeams; but the rule of belief in the changes of marine animals seems to be different, and so we have still people who cannot believe that a parr will some day become a salmon, or that the zoea will assuredly change into the highest order of crustacean life.

Perhaps, as we are now on the subject of crustacea, we may just remind the reader of the wonderful conditions of growth which are common to the greater number of our shell fish. Lobsters, crabs, shrimps, prawns, crayfish,—in fact, the crustaceans generally, have to change their shelly covering in order that they may increase in size. During the first year of their age the crab and lobster must change their suit of clothes more than once, they grow with such rapidity; but, as a rule, they have a new suit once a-year, and a wonderful power has been given them to throw off their old covering at the time of moulting. Crabs and lobsters have also the privilege of growing a new limb, whenever it is necessary for them to dispense with an old one, which they sometimes do in cases of fright or from accident. When from either cause a limb is destroyed, nature supplies a new one with great rapidity, either at once, or on the first occasion of exuviation.

Returning to the Salmonidæ, there are several interesting points in the biography of Salmo Salar that deserve mention, because every phase in the life of that king of fishes has been productive of controversy. Where does the salmon go to when it reaches the salt water? What is the cause of its going to the sea at all? What does it find to feed upon, and how quick does it grow? are slight samples of the questions which have been asked in reference to salmon growth. At one time wise people abounded who could answer these and similar queries off-hand, as it were; and one of the gravest assertions of the old writers about the salmon was, that the smelt, on arriving at the salt water, went off direct, and at lightning speed to the North Pole; a place where the common herring was also supposed to be a constant visitor. The real truth, however, is, that no one knows where the salmon goes to when it reaches the sea;—whether it proceeds to a great distance, or finds a luxuriant feeding-ground in the nearest deep water, has never been properly ascertained, but that it grows rapidly under the influence of the brine is certain. The curious instinct which leads the salmon, at certain seasons, to seek the salt water, and then to return to its native stream in order to perpetuate its kind, is another of the mysteries of salmon growth upon which different ideas prevail. It is said, that while in the salt water the salmon becomes infested with parasites of the crustacean kind, which it cannot get quit of till it reaches its native streams, or at least the fresh-water. Then, again, a kind of fresh-water louse fastens upon the animal in the river that is supposed to force it seaward; doubtless, however, these are but weak inventions of man to account for phases of life which are the nature of the animal, and which it was created to undergo. The sea seems to provide a rich feeding-ground for the salmon, for it returns home improved in condition and increased in size. Many of the smelts liberated from the breeding ponds at Stormontfield were marked, in order to ascertain how long they would be absent, and at what rate they increased in size. These points have been from time to time pretty satisfactorily detailed. It will be found, for instance, that a moiety of the salmon born in March of the present year (1863) will go off to sea as smelts in the months of April and May, 1864; and that in the autumn of that year they will come back as pretty sizeable grilses, whilst the half of their brothers and sisters will be still in the breeding-ponds as parr! Smelts a few ounces in weight, when liberated, or marked in April (we speak now of the river Shin experiments), have been recaptured in the month of July, after having attained a weight of from four to seven pounds. It was thought at one time that grilses never became salmon; indeed, the assertion was very recently reiterated; but the point was firmly settled years ago by the Duke of Athole marking a great number of fish while in their grilse stage; and as salmon almost invariably return to their parent stream, it became an easy matter to note the capture of the marked animals, and observe the rate of growth, which was in every case found to be remarkable. A specimen marked on February 18th of a particular year, and then weighing