348 HyJrflf, or Fresh-*iioater Polypus, 



to some increase of its thickness \ not, however, by the addi- 

 tion of any new layers, but by the effusion of vitreous matter. 

 Hence holes and canalss previously visible, are now filled up ; 

 the aperture contracted, and the margins strengthened and 

 enlarged; the upper part of the spire, perhaps, filled and 

 made solid ; and the peculiarities which distinguish the sexes 

 of the dioecious species fully developed. Foreign agents now 

 begin to act, and the external layers lose their hair4ike coat- 

 ing or their epidermis ; the colours become paler, and ulti- 

 mately disappear ; striae and tubercles are smoothed and worn 

 down ; and parasites deform and perforate the outer surface. 

 Death at length overtakes the architect, and the shell decays 

 under the influences of the water and of the air. 



Such, then, is the manner in which shells are formed, so 

 beautifully painted, and so curiously fashioned. They are the 

 house and strong hold of their proprietors, to whose exist- 

 ence, amid the strife of elements, and the wiles and voracity 

 of their foes, they seem essentially necessary. The shells of 

 the marine tribes, as was fit, are in general of great strength 

 and hardness ; or, if defective in these qualities, their weak- 

 ness, through the appliance of other means, is made strength. 

 The river kinds are less hard, and thinner, being less exposed 

 to the danger of a stormy element and a rocky bottom ; while 

 the shells of land snails are both light and thin, yet com- 

 pletely impervious either to moisture or air. There is much 

 to admire in all this : in the fitness of the shell to its element, 

 in the art displayed in the building, and in the painting of the 

 edifice, there is much to admire ; and yet the possessor crawls 

 on, unconscious of all, admiring nought. Wherefore, then, 

 this profusion of beauty ? Surely the Creator hath pleasure 

 in his works ; surely Epictetus speaks the language of reason 

 when he says, " God hath introduced man into the world to 

 be the spectator of his works, and of their divine Author ; and 

 not to be the spectator only, but to be the announcer and 

 interpreter of the wonders which he sees and adores." 



I am. Sir, &c. G. J. 



Art. IX. On tJw H^dra, or Fresh-water Polypus. By Samuel 

 Woodward, Esq. 



Sir, 

 I AM not aware that the subject of the il/ydra, or fresh- 

 water polypus, has been particularly noticed since the elabo- 

 rate treatise published by Henry Baker, Esq. F.R.S., in IT^S ; 

 and, that work having become scarce, a few remarks may be 

 interesting to your readers. 



