FISHES. 



559 



to the shore, and there the fish are found in great numbers iii 

 the plashes that still continue to have water in them. In some 

 of these places the quantity is so great that they are left in shoals 

 on those swamps, dried up by the sun, and their putrefaction 

 contributes to render the country unhealthful. 



This power of increasing in these animals, exceeds our ideas, 

 as it would in a very short time outstrip all calculation. A 

 single herring, if suffered to multiply unmolested and undimin- 

 ished for twenty years, would show a progeny greater in bulk 

 than ten such globes as that we live upon. But happily the 

 balance of Nature is exactly preserved ; and their consumption 

 is equal to their fecundity. For this reason we are to consider 

 the porpoise, the shkrk, or the cod-fish, not in the light of plun- 

 derers and rivals, but of benefactors to mankind. Without their 

 assistance, the sea would soon become overcharged with the 

 burden of its own productions ; and that element, which at pre- 

 sent distributes health and plenty to the shore, would but load 

 it with putrefaction. 



In the propagation of all fish, some degree of warmth seems 

 absolutely necessary, not only to their preservation, but to the 

 advancement of their posterity. Their spawn is always deposit- 

 ed in those places where the sun beams may reach them, cither 

 at the bottom of shallow shores, or floating on the surface in 

 deeper waters. A small degree of heat answers all the purposes 

 of incubation, and the animal issues from the egg in its state of 

 perfect formation, never to undergo any succeeding change. 



Yet, still I have some doubts whether most fish come from 

 the egg completely formed. AVe know that in all the frog tribe, 

 and many of the lizard kind, they are produced from the egg in 

 an im])erfect form. The tadpole, or young frog, with its enor- 

 mous head and slender tail, are well known ; a species of the lizard 

 also, which is excluded from the shell without legs, only acquires 

 them by degrees, and not till after some time does it put off its 

 serpent form. It is probable that some kinds of fish in like 

 manner suffer a change ; and though it be too inconsiderable to 

 strike the fisherman or the inattentive spectator, yet it makes a 

 very material difrercnce to the naturalist, and would, perhaps, 

 disarrange his most favourite systems. A slight alteration in the 

 fins or bones that cover the gills would overturn the whole fabric 

 ol the most applauded ichthyologist ; and yet, as I observed, 



