358 THE WATER-BEETLE. 



must be mistaken ; and that, if we attempt to reason 

 from foundations of that kind, we are umpires, and not 

 philosophers. 



The usual way in which water insects, and indeed 

 aquatic animals of all kinds, take, to fasten together 

 protection for themselves or their progeny, is not the 

 spinning of threads, but cementation by some fluid; 

 which, though it holds chips, straws, grains of sand, 

 or other solid substances together, and resists the motion 

 of the water, when used in small quantities as a mortar, 

 does not seem capable of resisting that action when in 

 the state of a slender filament, however well such a 

 filament may resist the action of the air ; and unless 

 we actually see an aquatic animal deviating from that 

 general habit, and actually spinning a cocoon, we have 

 a right to contend that such is never the case. 



The hatching of the eggs of the plunger has not, as 

 we have said, been observed through every stage of the 

 process. When, however, the larvse make their appear- 

 ance, they are not to be mistaken, either in their form 

 or their habits. They are well adapted both for running 

 and for swimming. The body is about double the 

 length of that of the full-grown beetle, formed into 

 joints or rings, the last of which tapers to a point, where 

 the body of the animal is formed round, not unlike the 

 tail of an eel ; there are six legs, which have crooked 

 claws at the extremities, and are beset with spiny fringes, 

 so that they answer the purpose either of feet or of fins. 

 The most remarkable and formidable part about it, 

 however, is the head, which is large, flat, and strong, 

 and furnished with a very powerful pair of forceps, each 

 in shape not unlike the tooth of an elephant, but more 



