*54 
SPINOUS FISHES. 
rant fertility, that the herring, the pilchard, and fome 
others, are obliged to migrate annually, from the artic 
regions, in Ihoals of fuch vail extent, that for miles they 
are feen to darken the furface of the water. 
But the amazing propagation of fillies, which we wit- 
nefs along our coalts and rivers, bears no proportion to 
the vaft quantities that fwarm in the warmer latitudes of 
the Indian ocean. The inhabitants of fome of the lflands 
there, are, it is faid, under no neceflity of providing in- 
ftruments for fiftiing : As they approach the Ihore, they 
are found in great numbers, in the plalhes, where ths 
water remains after the ebbing of the tide. In fome 
places where thefe fwamps are dried up by the fun, the 
fillies are left in fuch Ihoals, that they communicate by 
their putrefa&ion, a noxious and unhealthy tinfture to 
the atmofphere. 
Happily, however, for the purity of that element, and 
the health of thofe beings which it fupports in life, the 
wafte of thefe fifties is nearly proportioned to their fecun- 
dity ; and the balance of nature is exactly preferved- 
The lliark, the porpefib, and the cod, we ought there- 
fore to confider not fo much in the light of plunderers and 
rivals, as that of bencfaftqrs to mankind : Without 
their exertions, the fea would foon be overcharged with 
the burthen of its own inhabitants ; and that element, 
-which at prelent dillributes health and plenty to the 
ihore, would in a fliort time load it with putrefaction * • 
The generation and growth of fifties, and particularly 
of the oviparous, are involved in great obfcurity. The 
common opinion, as we have already Hated, is, that in 1 ' 
pregnatioi 1 
* Idem ubi fupra. 
