the nourishment, respiration, and reproduction of the animal, are not produced by the alleged irritability of its axis, nor by the supposed systole and diastole of its apertures, but by certain minute organs disposed over the whole surface of the internal canals. I have described the most striking differences which I have observed in the chemical constitution and microscopical forms of the minute parts composing the skeleton of this animal, in the three great tribes of horny, calcareous, and silicious species, and their beautiful arrangements to maintain the general form of the zoophyte, and to support and defend its soft parts. I have stated the characteristic properties and appearances of the connecting matter of the spicula, the parenchymatous, or general cellular substance of the body, the gelatinous net-works of the pores, and the granular bodies of the internal canals. I have examined the successive changes which the ova undergo from the time of their first appearance in the parenchymatous substance of the parent till their full development, and their expulsion from the fecal orifices, the causes of the singular spontaneous motions they exhibit, from the time of their expulsion till their metamorphosis into fixed inert zoophytes, and the progress of their growth in this fixed state, till they attain the perfect form of the parent. And, lastly, I have stated a few observations on their geographical distribution, and their purposes in the economy of nature. The uses of the central cavities in the horny fibres, and in the earthy spicula, and the different forms of these elementary parts, in all the known species ; -the mode in which the animal imbibes nourishment through the parietes of the internal canals, and the chemical changes produced on the fluid by its transmission through these passages;-the particular tribes of infusoria and more perfect animals that infest the different species, and depend on them for subsistence, and the applications of the earthy species of this animal to useful purposes in the arts, are still unknown. No one has yet excited to action any part of the adult animal, and the moving organs of the currents have never been seen. The mode of generation of this animal, and the structure of its soft parts, have yet been examined only in a very few species. The characters and the geological distribution of its organic remains have yet to be investigated, and probably not a tenth part of

the existing species have yet been brought to light from their recesses in the depths of the ocean. This animal still affords

many curious and interesting subjects of inquiry to those who have leisure and opportunities of examining the more perfect species of tropical seas; and, though probably the simplest of animal organisations, the investigation of its living habits, its structure and vital phenomena, and the distinguishing characters of its innumerable polymorphous species, is peculiarly calculated to illuminate the most obscure part of zoology, to exercise and invigorate our intellectual and physical powers, and to gratify the mind with the discovery of new scenes of infinite wisdom in the economy of Nature.

PLATE I

Fig. 1. Silicious, double-pointed, curved spiculum of the Spongilla friabilis. (See Edin. Phil. Jour. vol. xiv. p. 279.) This and the following 19 figures are magnified 50 times. Fig. 2. Silicious, fusiform, curved spiculum of the Spongia papillaris. (See Edin. New Phil. Jour. vol. i. p. 346). This spiculum occurs in Spongia tomentosa, or urens, S. cristata, and large in S. coalita.

Fig. 3. Silicious, double-pointed, curved, short spiculum of the Spongia cinerea, Gr. (See zoological notices at the end of the present Number.) This spiculum occurs half as large in S. oculata, S. palmata, S. dichotoma, S. prolifera, and S. cancellata, Sowerby.

Fig. 4. Silicious, single-pointed, straight spiculum of the Spongia panicea. (See Edin. New Phil. Jour. vol. i. p. 347.) This spiculum occurs slightly curved in the S. parasitica, Mont.

Fig. 5. Silicious, long, waved filament, obtuse at both ends, of the Spongia ventilabrum (see Edin. New Phil. Jour. vol. i. p. 349.), occurs along with another silicious spiculum, similar to fig. 18.

Fig. 6. Silicious, single-pointed, curved, thick spiculum, with a round head on its obtuse end, of the Spongia patera. (See Edin. New Phil. Jour. vol. i. p. 348.)

Fig. 7. Silicious, single-pointed, curved, slender spiculum, with a round head on its obtuse end, of the Cliona celata. (See Edin. New Phil. Jour. vol. i. p. 80.)

Fig. 8. Silicious, single-pointed, straight, moniliform spiculum of the Spongia monile, Gr. (See Edin. New Phil. Jour. vol. i. p. 348.)

Fig. 9. Silicious, single-pointed, curved, long spiculum of the Spongia sanguinea, Gr. (See zoological notices at the end of the present Number.)

Fig. 10. Silicious, curved, short spiculum, obtuse at both ends, of the Spongia fruticosa. (See Edin. New Phil. Jour. vol. i. p. 350.) For the S. hispida the same form occurs, but more than double this length.

Fig. 11. Calcareous triradiate spiculum of the Spongia compressa. (See Edin. New Phil. Jour. vol. i. p. 166.)

Fig. 12. Calcareous, clavate, curved spiculum of the S. compressa. (Ibid.)

Fig. 13. Calcareous, straight, very minute spicula of the S. compressa. (Ibid.)

Fig. 14. Calcareous, triradiate, large spiculum of the Spongia nivea. (Ibid. p. 168.)

Fig. 15. Calcareous, quadriradiate, minute spiculum of the S. nivea. (Ibid.)

Fig. 16. Calcareous minute fragments of triradiate spicula of the S. nivea. (Ibid.)

Fig. 17. Calcareous triradiate slender spiculum of the Spongia (Ibid. p. 170.)

coronata.

Fig. 18. Calcareous, single-pointed, slightly curved long spiculum of the S, coronata. (Ibid.)

Fig. 19. Horny tubular thick fibres of the Spongia fistularis. (See Edin. Phil. Jour. vol. xiv. p. 339.) a. Amber-coloured horny translucent parietes. b. Dark opaque granular matter filling the central cavity.

Fig. 20. Horny tubular thin fibres of the Spongia communis. (Ibid.) a. Amber-coloured transparent parietes. b. Empty central cavity.

Fig. 21. Living Spongia papillaris under water, shewing its mode of generation, &c. (See Edin. New Phil. Jour. vol. ii. p. 133.) a, a, Minute pores through which the currents enter. b, Commencement of the internal canals. c, Uniting of the internal canals to form a fecal orifice. d, A fecal orifice discharging a current of water with feculent matter. e, A fecal orifice discharging two ova and feculent matter with the current. ff, Groups of mature ova. g, Ovum passing into a canal. h, Gelatinous base connecting this animal to the rocks.

Fig. 22. Living Spongia oculata, shewing its currents, mode of generation, &c. a, a, Minute pores transmitting water obliquely into the canals. b, b, Fecal orifices discharging currents, feculent matter, and ova. c, Strong fibrous part of the animal

by which it hangs from rocks. Fig. 23. Living Spongia compressa, with a part of its side laid open, to shew the terminations of its canals in the interior of its general cavity. a, Expanded base by which it hangs from rocks, fuci, &c. b, Compressed terminal opening of its general cavity, by which the currents, ova, and feculent matter, finally escape. c, Minute pores by which the water passes obliquely through its parietes. d, A part laid open, to shew the fecal orifices terminating in the general cavity of the animal.

Fig. 24. A pore of the Spongia panicea highly magnified, to shew (a) its bounding fasciculi, and (b) a defending fasciculus spread over a gelatinous network.

Fig. 25. A pore of the Spongia papillaris highly magnified, to shew (a) its bounding fasciculi, (b) the part where the bounding fasciculi cross each other to form recesses for the ova, and to which the connecting matter of the spicula was supposed to be confined, and (c) the most usual appearance of the gelatinous network of the pores in this species.

Fig. 26. A transverse section of an internal canal of the Spongia papillaris. a, Its bounding fasciculi, covered with the very minute monade-like bodies composing the parenchymatous matter. b, Groups of imperfectly formed ova lying in recesses of the parenchymatous matter. c, Simplest form of the gelatinous network found within the canals. d, Ova hanging by their tapering extremity to the side of the internal canal, and producing currents by the motions of the cilia covering their free surface.

Fig. 27. Highly magnified ovum of the Spongia panicea, viewed from above, when about to fix. a, Central opaque part occupied by spicula, and covered with ciliæ. b, Zone of vibrating ciliæ distinctly seen round the margin. lated sediment, produced by the cilia

c, Zone of accumuconstantly clearing the

Fig. 28. Highly magnified ovum of the Spongia panicea, viewed laterally, to shew its entire ovate form. a, Ciliæ, longest on the vertex of the ovum, and resting on a more translucent part of the ovum. b, White pellucid base by which the ovum fixes

1

and expands.

c, The part where the white base commences,

and where the cilia seem to terminate.

Fig. 29. Appearance of the young Spongia panicea, after the ovum has fixed and spread for fourteen days on a watch-glass. a, Central opaque part to which the spicula were at first confined. b, Transparent homogeneous margin by which the young sponge spreads, and which likewise produces spicula. c, Halo of accumulated sediment frequently seen round the margin, at a little distance from the young sponge, and inclosing a cleared space, as in Fig. 27. d, The part where the monade-like parenchymatous matter terminates, and where the colourless homogeneous matter commences.

Enumeration of the Instruments requisite for Meteorological Observations; with Remarks on the mode of conducting such Observations. By Professor LESLIE

EVERY meteorological observatory, if it shall register with

accuracy, and in a complete and satisfactory manner, the various atmospheric phenomena, ought to be provided with the following instruments.

1. The barometer, which measures the pressure of the atmosphere; 2. The thermometer, which indicates its degree of heat; 3. The hygrometer, which marks its relative dryness; 4. The atmometer, which measures the quantity that evaporates in a given time from the surface of the earth; 5. The photometer, which indicates the intensity of the light transmitted from the sun, or reflected from the sky; 6. The athrioscope, which detects the cold showered down from the chill regions of the higher atmosphere; 7. The cyanometer, which designates the gradation of blue tints in the sky; 8. The anemometer, which measures the force and velocity of the wind; 9. The ombrometer or rain-gauge, which marks the daily fall of rain, or haill, or snow; 10. The electrometer, which indicates the electrical state of the air;

* In a close room or sheltered in external air, the atmometer might supply the place of an hygrometer; and compared with another one freely exposed, it might serve as a substitute for the anemometer.