OR, PLAIN TEACHING. 



337 



place a snail upon a piece of 

 glass, and wait until it crawls, 

 then we may see plainly the cu- 

 rious working of this rudimen- 

 tary organ. The matter which 

 forms the shells of snails is se- 

 creted by their bodies, and the 

 shells grow with the increase of 

 size of the animal. 



As soon as the first autumnal chills are felt, 

 snails become indolent, lose their appetites, and 

 associate in considerable numbers on hillocks, 

 the banks of ditches, thickets, hedges, and 

 similar places. In a short time they cease 

 feeding, and then hide themselves under moss, 

 grass, dead leaves, and the like. Here each 

 forms for itself with the anterior part of its 

 muscular foot a cavity sufficiently large to con- 

 tain at least its shell; this cavity it enlarges 

 and excavates by turning itself round on every 

 side, then raising itself against the sides of the 

 cavity, and at last against the roof formed of 

 moss or leaves, or a small quantity of earth 

 brought there by its motions. When it has 

 succeeded in bringing the aperture of the shell 

 to nearly a horizontal position, it stops. The 

 foot is soon contracted within the shell, the 

 snail then expands, so as completely to cover 

 the collar of the mantle, which is at this period 

 very white ; and then inspires a quantity of 

 air, after which it closes the respiratory hole 

 When this is done, a fine transparent membrane 

 is formed with its mucus, and interposed be- 

 tween the mantle and any extraneous substances 

 lying above. The mantle then secretes a quan- 

 tity of very white fluid over its whole surface, 

 which sets uniformly, like plaster of Paris, and 

 instantly- forming a continuous covering about 

 half a line thick. When this is hardened, the 

 animal separates its mantle from it by another 

 and stronger mucous secretion ; and after a 

 few hours, expelling a portion of the air it had 

 previously inspired, it is enabled to shrink a 

 little farther into the shell. It* now forms 

 another lamina of mucus, expires more air, 

 and thus retires farther into the shell In this 

 way sometimes a fourth, fifth, and even a sixth 

 partition is formed, with intermediate cells 

 filled with air. 



In the centre of the lamina 

 closing the shell in winter is a 

 little hole or holes, too small to 

 admit water, but sufficient to 

 allow air to pass for the purpose 

 of respiration. 



Snails lay eggs, and carefully 

 bury them in the ground. These 

 eggs are very numerous, round, 

 semi-transparent, about the size 

 of a small pea, and covered with 



1 



soft shells : they are also united 

 to each other by an imperceptible 

 slime. When the snail leaves 

 the egg, it is observed with a 

 very small shell on its back, 

 having only one whorl ; but, in 

 proportion as it grows, the shell 

 increases in the number of its 

 spiral turns. The addition is 

 always at the mouth, the first 

 centre still remaining ; the 

 animal sending forth from its 

 body that slime which hardens 

 into a calcareous substance, and 

 is still fashioned into similar 

 convolutions. Thus fitted with 

 its covering, which is light and 

 firm, the snail finds itself well 

 defended from external injury; 

 and it has only to retire into its 

 fortress to escape impending 

 danger. It derives its chief sub- 

 sistence from the leaves of plants 

 and trees, and although very 

 voracious, is extremely delicate 

 in its choice* 



While rambling in our garden, 

 our attention may probably be 

 called to those interesting little 

 creatures, ants. Their name is 

 a vulgar contraction or perver- 

 sion of the original Saxon word 

 asmet, or emmet, the well-known 

 insect, the emmet, a genus of 

 insects of the hymenopteral order, 

 a membraneous - winged insect, 

 whose characteristics are a small 

 scale between the breast and 

 belly, with a joint so deep that 

 the insect appears aimost cut into 

 two ; each species consisting of 

 three distinct sets or classes of 

 individuals — the males, females, 

 and the neuters, the last being 

 females with imperfect organiza- 

 tion. We shall be compelled to 

 5 



