OF INSECTS. 195 



one and the same purpose is attained. In the article of 

 breathing, for example, which was to be provided for in. 

 some way or other, besides the ordinary varieties of lungs 

 gills, and breathing-holes, (for insects in general respire, 

 not by the mouth, \FI XXXIII. fig. 7.) but through holes 

 in the sides,) the nymphsB of gnats have an apparatus to 

 raise their backs to the top of the water, and so take breath. 

 (PL XXXIII, fig. 8.) The hydrocanthari do the like by 

 thrusting their tails out of the water.* The maggot of the 

 eruca labra, (PI. XXXIII. fig. 9.) has a long tail, one part 

 sheathed within another, (but which it can draw out at 

 pleasure,) with a starry tuft at the end, by which tuft, 

 when expanded upon the surface, the insect both supports 

 itself ifi the water, and draws in the air which is necessary. 

 In tlie article of natural clothing, we have the skins of ani- 

 mals invested with scales, hair, feathers, mucus, froth ; or 

 itself turned in a shell or crust; in the no less necessary 

 article of offence and defence, we have teeth, talons, beaks,, 

 horns, stings, prickles, with (the most singular expedient 

 for the same purpose) the power of giving the electric 

 shock, f and as is credibly related of some animals, of 

 driving away their pursuers by an intolerable fo&tor, or of 

 blackening the water| through which they are pursued. 

 The consideration of these appearances might induce us to 

 believe that varieti/ itself, distinct from every other reason, 

 was a motive in the mind of the Creator, or with the 

 agents of his will. 



* Derham, p. 7. 



t The raja torpedo, gymnotus electricuSf and some other fish, have 

 a curious apparatus of nerves, which, iq its effects, may be compared 

 to an electrical battery. In the first named ^is^, the electrical organs 

 are situated between the head and the pectoral fins. When the inte- 

 guments are raised, the organ appears, consisting of some hundred 

 pentagonal and hexagonal cells, filled with a glairy fluid. Minute 

 blood-vessels are dispersed over it, and its nerves are of extraordinary 

 size. When the hand is applied to the electrical organs, a benumbing 

 effect is instantly felt in the fingers and the arm. When caught in a 

 net, it has been known to give a violent shock to the hands of the fish- 

 erman who ventures to seize it. Pkil. Trans. 1816. p. 120. and 1817, 

 p. 32. Paxton. 



t The several species of sepia or cuttle fish, have this faculty. 

 They possess a bag situated on, or near the liver, called the ink-hag, 

 from its containing a black fluid, the contents of which is discharged 

 by a muscular sheath compressing the body of the animal. By this 

 singular evacuation, the creature renders the surrounding element so 

 black and bitter, when in danger of being attacked, that an enemy 

 will not pursue it. lb. 



