294 NATURAL THEOLOGY. 



the pupil to the object. This great defect is, how- 

 ever, perfectly cojiij^ensated, and by a mechanism 

 which we should not suspect. The eye is a mul- 

 tiplying-glass with a lens looking in every direc- 



under a silken hood or tube, six eyes only projecting. Some bore 

 a hole in the earth, and line it as finely as if it were done with the 

 trowel and mortar, and then hang it with delicate curtains. A very 

 extraordinary degree of contrivance is exhibited in the trap-door 

 spider. This door, from which it derives its name, has a frame 

 and hinge on the mouth of the cell, and is so provided that the 

 claw of the spider can lay hold of it, and whether she enters or 

 goes out, says Mr. Kerby, the door shuts of itself. But the water 

 spider has a domicil more curious still : it is under water, 

 with an opening at the lower part for her exit and entrance ; and 

 although this cell be under water, it contains air like a diving-bell, 

 so that the spider breathes the atmosphere. The air is renewed 

 in the cell in a manner not easily explained. The spider comes 

 to the surface ; a bubble of air is attracted to its body ; with this 

 air she descends, and gets under her cell, w^here the air is disenga- 

 ged and rises into the cell ; and thus, though under water, she lives 

 in the air. There must be some peculiar property of the surface 

 of this creature by which she can move in the water surrounded 

 ^^ ith an atmosphere, and live under the water breatliing the air. 



The chief instrument by which the spider performs these won- 

 ders is the spinning apparatus. The matter from which the threads 

 are spun is a liquid contained in cells ; the ducts from these cells 

 open upon little projecting teats, and the atmosphere has so imme- 

 diate an effect upon this liquid, that upon exposure to it, the secre- 

 tion becomes a tough and strong thread. Twenty four of these 

 fine strands form together a thread of the tliickness of that of the 

 silk-worm. We are assured that there are three different sorts of 

 material thus produced, which are indeed required for the various 

 purposes to which they are applied — as, for example, to mix up 

 the earth to form the cells, — to line these cells as with fine cotton, 

 — to make light and floating threads by which they may be con- 

 veyed through the air, as well as those meshes which are so geo- 

 metrically and correctly formed to entrap their prey. 



