It has, I believe, been generally observed, that the more simple the organization of animals, the more retentive is the creature of life, and this is the case with these minute beings. The _Rotifer vulgaris_ will even bear revivification several times. Dr. Carpenter relates that he tried the experiment six times with twelve specimens, and each time some were perfectly restored to animation. By allowing the drop of water which held them to evaporate, and at the end of twenty-four hours giving them a fresh supply, he succeeded six times in restoring some of them: at last two only were left, and these unfortunately he lost. Ehrenberg affirms, that if thoroughly desiccated they can not revive, but that they may remain in a lethargic condition if deprived of water for a certain time only. The same naturalist observes that when an animalcule is frozen with the water, it is surrounded by an exceedingly small portion which is unfrozen, occasioned probably by the animal heat of its body; but, should the cold be so great as to freeze this, the creature dies. Animal heat in such an atom! how marvelous! Yet they will bear a great degree of heat also. The same naturalist says, that the _Polygastrica_, will bear the temperature _gradually_ raised to 120° of Fahrenheit, and some even to 200°, but if raised _suddenly_ they die at 140°. Now, if we consider that water raised to 212° is boiling, we shall be as much astonished at their powers of enduring heat as cold. Sir James Ross, in his Antarctic Expedition, found upward of seventy species of _Polygastrica_ with _loricæ_, or silicious shells, in fragments of ice. It will, therefore, be seen, that animalcules are obtainable at all seasons, and in every place where there are ponds or pools of water; or they may be procured from water-butts, or by placing leaves, hay, or almost any vegetable substance in a little water, which has been previously found to have nothing living in it. EDWARD DRYSDALE. A LEAF FROM THE DIARY OF A LAW-CLERK.