may serve to direct the attention of those who have more frequent opportunities of observing the habits of fishes than my other engagements allow me. .

Most of the objects represented in the engraving, Plate IV., have been explained already in the course of the foregoing account. Fig. 1. represents the æsophagus and sto mach, the former with its papillæ, the latter with its curvatures; and a more complete view of the direction of these curvatures is given in Fig. 5. Fig. 2. exhibits the pancreatoid organ, the pylorus, and the duodenum, with the reticular structure of its inner membrane. Fig. 3. shews the intestine with the spiral valve; A A, the axis or central column; rrr, the reticular cells on its right side; and 11), the smooth ones on its left. Fig. 4. is the posterior margin of the orifice into the swimming bladder. And in Fig. 6. are seen the four openings, the anus (a) and urethra (n), on the mesial plane, and the lateral peritoneal orifices (oo) on each side.

XIII.- Observations on the Aranea geometrica,

obtextrix, domestica, and other Spiders; and particularly on the power they possess of fixing their threads horizontally, or at any degree of inclination, to two perpendicular bodies at a considerable distance from each other, so as to suspend the circular part of their web in an open space: Also some remarks on the Food of Spiders, &c.

By MARK WATT, Esq. M. W. S.

( Read 6th February 1830.)

a

It was in consequence of observing it stated in the first edition of Kirby and Spence's Introduction to Entomo. logy, that it was not known how the garden or geometric spider attached the long lines which supported its web to two upright bodies at various distances from each other, and at a considerable elevation above the surface of the ground, that I made a number of experiments to ascertain how this was accomplished, and the result of these experiments was published in a short paper, in April 1817, in Dr Thomson's Annals of Philosophy

The observations I have since made confirm what I then expressed, viz. that it is quite indubitable that the geometric spider has the power, either in a room or in the open air, when the atmosphere is calm, of throwing out its thread with great rapidity to the length of several feet or yards, and in such a manner as to strike against a particular part of any body that may be within the reach of the thread. I have very often observed the geometric spiders in the act of performing this curious operation; and I can affirm, that the larger individuals seem to be able to hit any spot they intend to attach the end of their thread to, with almost the same precision that the jaculator fish strikes a fly with the drop of water it ejects from its mouth. Indeed, the regular disposition of the threads that radiate from the centre of the web of these spiders, is a proof that they must be capable of directing their lines to a given point, as these threads are often five and six feet long.

The method I at first adopted to discover this very in- . teresting faculty of the spider, was to place a pretty large stone in the centre of a broad plate, and fill the plate with water, leaving the upper part of the stone dry: then by means of a little clay or putty I placed a slip of wood or a straw, a foot or two high, perpendicularly on the stone; some spiders were then placed on the dry part of the stone. By this method I perceived the spiders, which have an aversion to the water (as they cannot move upon it), make their escape from the confinement, by the upper end of the piece of wood, or the straw.

After examining the circumstances of their situation, they uniformly had recourse to one of two methods by which they made their escape. They either let themselves drop down by their lines about two inches from the top of the stick, and, turning their spinners towards the wall of the apartment, they threw out their threads with great rapidity till they touched the wall, where they stuck, and the instant they struck the wall, they turned round and fastened the other ends of the threads to the stick, and thus ran across ;-or they ejected a line upwards, which its buoyancy,