assisted by a good microscope, may open up still more satisfactory views of the subject. With respect to the other two species, I can speak with less precision; I shall state, however, what I believe to have ascertained, though I shall not venture to speak undoubtingly. The Ulva dichotoma has a reticulated texture, which, as Lightfoot observes, gives it the appearance, when magnified, of belonging to the genus Flústra of corallines. Now it appeared to me, when examining portions of this plant under the influence of fresh water, and in the field of an Ellis's microscope, that each of the cells which cause the reticulated appearance was covered by a membranous lid, which, from the presence of the fresh water, burst up with violence. On examining Fucus punctatus in the same way, soon after its first contact with fresh water, I could perceive a very evident jerking motion occurring here and there over its surface, with an appearance as if little facets or scales had been suddenly let loose, like the lid of a hunting watch when the spring is pressed. I must observe, however, that what I have stated of these last two plants is to be considered as only an introductory view of the subject, and that farther investigation will be necessary to give absolute certainty. At the same time the analogy between the phenomena presented by the three species mentioned is so strong, that there can be little doubt of their being regulated by the same law. I believe the U'lva dichotoma gets paler by immersion in fresh water; but of this I am not prepared to speak positively. Respecting the other two species there can be no hesitation, they both give out their colouring matter copiously to the fresh water in which they are placed, and that in a very short time. If the Conférva setacea be spread on paper in sea water, it retains its original hue; there is no bursting up of its septa, nor breaches in its sides, and it does not tinge the paper on which it is spread. I have preserved a number of specimens in this way. Fucus punctatus, when preserved in the same manner, retains its original deep hue, and does not tinge the paper. The flaccidity which takes place in them all is scarcely to be accounted for, except on the principle that their texture is in some respect broken up, and we may presume also that, as in Conférva setacea, both the other species explode the contents of their cells or cavities. The circumstance of these plants giving out their colouring matter to the paper on which they are spread has been often remarked, but has never before, I apprehend, been suspected, of being connected with their vitality. That it is so, however, the observations made above clearly demonstrate. For it is not because the plant is dead that the colouring matter is given out, but, on the contrary, because it is living; and it appears to me that the phenomena exhibited by the Conférva setacea, when immersed in fresh water, are very analogous to those of the Lurg-worm. It is a living body labouring under the effects of poison; and the bursting up of its septa, the breaches formed in its sides, the curdling, and spasmodic explosion of its colouring matter, are, like the convulsions of the worm, the symptoms which characterise its expiring struggles in the arms of a deadly foe. It is obvious that what I have said respecting the dissemination of the Lurg-worm will equally apply to these plants. The ocean is their prescribed element, and they can never appear under any form or variety in lakes, rivers, or any collection of fresh water whatever. How extensive the field may be which these remarks are calculated to lead to I cannot conjecture: but I apprehend there can be little doubt that many interesting facts of an analogous kind remain in store for future observation; and I hope that I may again have an opportunity of laying before the Society farther information on this subject. ART. II. Indications of Spring. By Robert Marsham, Esq., and Lord Suffield. Communicated by R. C. TAYLOR, Esq. F.G.S. THE following Table of the "indications of spring" contains the result of more than sixty years' observation, by Robert Marsham, Esq., of Stratton Strawless, in the county of Norfolk; a gentleman of whom it need scarcely be premised that he was an attentive and accurate observer of the phenomena of nature. In this work he probably derived some assistance, latterly, from his neighbour Lord Suffield. Stratton Hall, where Mr. Marsham recorded his remarks, is nearly in the centre of Norfolk, and its neighbourhood was greatly embellished by the judicious skill which he exhibited in the rural art of planting. The Table was printed for private distribution many years ago, but I am not aware that it was otherwise published. At all events the register is so curious and so appropriate to the design of your Magazine, that it well deserves an early place in its pages. I have introduced an essential alteration in the arrangement, for the sake of a better classification of the indications. To the meteorologist, also, this document cannot fail to be acceptable, since it marks the range of variation in the climate of the eastern part of the kingdom. The earliest date recorded is the year 1735, and the latest observation appears in 1800. The least variation is in the time of the appearance of the migratory birds, and the hatching of young rooks. The greatest range is in the blossoming of the turnip, the appearance of the yellow butterfly, and the singing of the thrush. Nightingale sings INDICATIONS OF SPRING. Thrush sings....... Churn Owl sings..... 1735, Dec. 4. .... 1779, Mar. 5. Hornbeam leaf.............. 1794, Mar. 7. 1779, April 2. 1794, Mar. 19. 1794, Mar. 15. 1766, Feb. 13. 1758, Mar. 19. 1744, May 12. 71 days. 1744, Mar. 30. 1745, Mar. 29. 63 days. 1773, April 6. 43 years-57 days. 1773, April 6. 1757, April 26. 1785, April 23. 1784, April 23. 1776, April 21. 1789, April 9. 1787, April 29. 1796, April 13. 1788, April 12. ge ART. III. The Cuvierian, or Natural, System of Zoology. Essay 3. The Characters of Vertebrated Animals, and their Division into Four Classes; Mammiferous Animals, Birds, Reptiles, and Fishes. Distinctive Characters of each Class. By B. HAVING given in the preceding essays Baron Cuvier's neral view of animal physiology, and stated the principles on which he establishes four grand divisions of the animal kingdom, I shall, in the present essay, comprise his more ample description of the characters of the first division, VERTEBRATED ANIMALS; also the distinctive characters of each of the four classes into which they are divided. It will be shown that this division into four classes is justly founded upon the internal organisation, and not upon the external forms, of animals; and the reader will not fail to perceive the importance, indeed the absolute necessity, of an acquaintance with the leading facts in animal physiology, if he would obtain a correct knowledge of zoology as a science. Vertebrated animals form the most important division of the animal kingdom. Their bodies and limbs being supported by a framework (charpente) or skeleton, composed of pieces which are connected or movable; their motions have more strength and precision than those of animals in the other divisions, and the solidity of their supports permits them to attain a great size: the largest animals are found in this division. The nervous system of vertebrated animals being more concentrated, and the central mass or brain more voluminous, than in animals in the other three divisions, their sensations (sentimens) have more energy and duration, hence they possess superior intelligence and greater perfectability. The body of vertebrated animals is composed of a head, a trunk, and limbs. The head is formed of the skull which encloses the brain, and of the face which is composed of two jaws, and the receptacles of the organs of sense. The trunk is supported by the backbone and the ribs. The backbone, or spine, is composed of numerous bones called vertebræ, moving upon each other; the first supports the head. All the vertebræ are perforated, and together they form a bony channel or tube, in which is lodged that trunk of the nervous system called the spinal marrow. The backbone is most frequently prolonged beyond the lower limbs, and forms a tail. The ribs are semicircles, which protect the sides of the cavity of the body; most frequently they are articulated at one end to the vertebræ, and at the other to the breastbone or sternum; sometimes they are scarcely visible. Vertebrated animals have never more than two pair of limbs; sometimes the hind limbs, and sometimes the fore limbs, and sometimes both pairs are wanting, and take other forms relating to the motions they have to perform. The fore limbs may be converted into hands, or feet, or legs, or fins; the hind limbs into feet or fins. The blood of vertebrated animals is always red, and has a composition proper to maintain the energy of feeling, and the muscular vigour which exist in different degrees in the animals belonging to this division, and which correspond with the quantity of respiration. The organs of the external senses are always two eyes, twò ears, two nostrils, the teguments or covering of the tongue, and those of the whole body. There are always two jaws: the principal motion is in the lower, which rises and falls; the upper is sometimes entirely fixed. Both jaws are most frequently armed with teeth, excrescences of a peculiar nature, very similar to bone in their chemical composition, but which increase by layers (couches) and by transudation. But one entire class, namely, birds, have their jaws covered with horny beaks, and this is the case with the genus tortoise in the class of reptiles. The above characters, which are chiefly external, would enable any person unacquainted with physiology to distinguish vertebrated animals from those in the other divisions. Some orders of articulated animals approach in form the nearest to vertebrated animals, but they have no internal skeleton. The characters derived from the internal structure and organisation are strictly physiological, and the learner must refer to what has been stated in the first and second essays respecting them. In the division of vertebrated animals, the nerves unite with the spinal cord through passages in the vertebræ, or in the skull: they appear all to unite into a double bundle (faisceau) which forms this spinal cord, and which, after having crossed its filaments, spreads and swells out to form the divers tubercles of which the brain is composed, and terminates in two medullary masses called hemispheres, the relative volume of which corresponds with the extent of intelligence. The intestinal canal extends from the mouth to the anus, undergoing, in its course, various expansions and contractions : it has different appendages, and receives different dissolving fluids. That which pours into the mouth is called the saliva; other fluids which enter the intestines have received different names; the two principal are the secretion from the gland called the pancreas, and the bile which is secreted by another very considerable gland called the liver. While the digested aliments traverse the 'alimentary canal, the part proper for nutrition, called the chyle, is absorbed by particular vessels called lacteals, and is carried into the veins; the residue of the nutrition is also carried into the veins by vessels analogous to the lacteals, forming with them one system, called the system of the lymphatic vessels. The veins bring back to the heart the blood which has served to nourish the different parts, and which has been renewed by the chyle and the lymph; but this blood is obliged to pass wholly, or in part, into the organ of respiration, to regain the nature of arterial blood by the absorption of oxygen, and by exhalation, before it is carried back into the arteries. In the first three classes of animals, the respiratory organs are lungs, an assemblage of cells into which the atmospheric air penetrates. In fishes the respiration is performed by gills, a series of lamina between which the water passes. |