80 
THE 
CANADIAN 
NATURALIST. 
behind close to his sides ; but I do not see how he moves ; he 
has no fins^ and it is not by means of his legs. 
F, — If you look closely, you may observe that previously 
to every motion the minute floating particles of earth, &c. rush 
in a current towards its tail, and are then forcibly driven away ; 
at which moment the insect shoots ahead. The tail of this 
grub is, in fact, a complete syringe, being furnished with a 
piston capable of being drawn towards the head, or thrust 
towards the tail, at will. On drawing it inward, the water 
rushes in ; then this piston is forcibly thrust downward, 
ejecting the contained water in a jet or stream, which, by the 
resistance of the surrounding fluid, throws the insect forward. 
If you hold it under water in your fingers, so as to see the 
tail, you may observe the operation. 
C. — The tail is composed of three triangular pieces, 
which meet exactly together, when shut ; and when open, 
show another valve opening outwardly when the water is 
ejected. What a curious contrivance ! 
F. — But you do not yet know the whole use of this sin- 
gular organ : it is a breathing apparatus as well as a means 
of locomotion ; and every inspiration of water is an act of 
respiration. The piston, as we call it, is composed of the 
trachem or air-vessels, whose office is to extract oxygen from 
the water, in the same manner as the gills of fishes. Here 
is additional matter for wonder : but wonder is not the only 
sentiment which such an organization should awaken in our 
minds : it surely calls for admiration of the infinite wis- 
dom of God the Creator, in thus adapting an organ to pur- 
poses so widely different ; while at the same time so per- 
fectly is each operation performed, that it would seem, on 
considering either of the two processes to be effected, as if the 
organ were created for that express purpose alone. Again, 
it gives us exalted ideas of the benevolence and all-pervading 
love of God, to observe such astonishing skill of contrivance 
displayed for the comfort of so mean a reptile ; a creature 
