latitie: this organ; it's aperture is from the gullet; 
and what air is injefted muft remain there till the 
receffities, and not the will of the animal, call it 
forth as afupply. 
However, to render this more evident, it is cer- 
tain, that many Filla which continually crawl at 
the bottom, fuch as the eel and the flounder, are 
furnifhed with air-bladders; and many are with- 
out any bladder, fuch as the anchovy and the gud- 
geon, which fwim at eafe in any depth. Indeed, 
the number of Fifli that want this organ feems 
alone a ilifficicnt proof that it is not neceiTary for 
the purpofes of fvvimming; and as the ventral fins, 
which in all Fifhes lie fiat on the water, feem fully 
fufficient to fupport them at all depths, they can 
have no abfolute occafion for this internal appara- 
tus to afiifi; them in rifing and finking. It m,ay, 
indeed, contribute to thofe purpofes ; but it is like- 
wife very probable, that it has another and a more 
importanc ufe. 
In every point of view in which we have re- 
garded Fiflies, they appear inferior to land ani- 
mals ; in the fimplicity of their conformation, in 
their fenfes, and in their enjoyments: but, as fome 
degree of compenfation, they enjoy that humble 
exiftence a much longer term than any other clafs 
of animated nature. ' Mofc of the diforders inci- 
dent to mankind,' fays Bacon, ' arife from the 
changes and alterations of the atmofphere:' but 
Filhes refide in an element little liable to change; 
theirs is an uniform exiftence; their movements 
are without effort, and their lives without labour. 
Their bones, aifo, which are united by cartilages, 
admit of indefinite extenfion; and the different 
fizes of animals of the fame kind among Fifhes 
are very various. They ftill keep growing; their 
bodies, inftead of experiencing the rigidity of age, 
which is the caufe of natural decay in land animals, 
ftill continue increafingwith frefn fupplies; and as 
their bodies grow, the conduits of life furniOi their 
ftores in greater abundance. How long a Filh, 
which feems to have fcarce any bounds prefcribed 
to it's growth, continues to live, is not afcertained ; 
perhaps the life of man would not be long enough 
to meafure that of the fmalleft. Two methods, 
which are more ingenious than certain, have been 
devifed for determining die age of Fifhes : the one 
is by the circles of the fcales ; the other by the tranf- 
verfe fetlion of the back-bone. By the firft me- 
thod, when the fcaleof a Fifli is examined through 
a microfcope, it will appear to confift of a number 
of circles, one within another: and, as in trees, 
their age is known by the number of circles in 
their tranfverfe feftion; fo, in Fifnes, we difcover 
their age by the number of circles in every fcale, 
reckoning one ring for every year. Bufibn found 
a carp, which, by this method of computation, 
appeared to be upwards of an hundred years 
old. Flowever incredible this may appear, the 
accounts of feveral authors of veracity tend to con- 
firm the difcovery. Gefner mentions one of the 
fame age; and Albertus brings an inftance of one 
which exifled upwards of double that period. 
The fcate and the ray, having no fcales, their 
ages may be found by the other method ; which is, 
by feparating the joints of the back-bone, and then 
examining the numiber of rings, which the fur- 
face, where it v;as joined, exhibits. 
For the certainty of thefe methods it is impof- 
fible to vouch ; but we have every reafon to be- 
lieve the extraordinary age of fome Fifnes. But 
the fecundity of thefe animals is more extraordi- 
nary than their longevity. Som.e produce their 
young alive, and others only eggs; the former are 
the leaft prolific, and yet they produce in amazing 
abundance. , The viviparous blenny, for inftance, 
produces two or three hundred at a time, whicli 
immediately divert themfeives by playing round 
their parent. Thofe v/hich exclude their progeny 
in eggs, and are obliged to leave them to chance, at 
the bottom of fhallow v/ater, or floating on the fur- 
face, where it is deeper, are much more prolific; 
their ftock being in fome micafure proportioned to 
the danger there is of it's confumption. But few of 
thefe eggs, in comparifon, produce animals, being 
devoured by Fiflies and aquatic birds : ftill, how- 
ever, the numbers that cfcape are fufficient to fup- 
ply the deep with inhabitants, and to relieve the 
vv^ants of a very confiderable part of mankind. 
The number that a Angle Fifli is capable of 
producing is almoft incredible. A fingle cod is 
laid to produce, in one feafon, as many of it's kind 
as there are inhabitants in England. Lev/enhoeck 
afilires us, that the cod fpav/ns above nine millions 
of eggs in one feafon ; and feveral other fpecies 
have a proportional increafe. But Mr. Harmer 
has lately purfued the inveftigation of this curious 
fubjeft with much more accuracy than any of his 
predecelTors, and has extended his enquiries to a 
greater variety of fpecies than any other perfon. 
The method Vv'hich he adopted was, that of weigh- 
ing the whole fpawn very exa6lly; he then took a 
piece weighing a certain number of grains, and 
carefully counted the eggs it contained; and by 
dividing the numiber of eggs by the number of 
grains, he found nearly how many eggs there were 
in one grain. His com.putation of the number of 
eggs extended no farther than to thofe which he 
could diftinguifh by the naked eye; though, by 
this limitation, he omitted many eggs difcoverable 
by a microfcope, which miight juftly have been 
thrown into the aggregate. The weights he ufed 
were avoirdupois, and he reckoned 437i- grains to 
an ounce. The fubfequent table exhibits the ge- 
neral refult of his enquiries; the fi.rft column con- 
taining the number of Fifhes which he examined; 
tiie fecond, their weight; the third, the weight of 
their fpawn; the fourth, their fecundity; and the 
fifth, the feafon of the year when each fpecies Vvas 
examined. Fie has alfo added other columns, 
exhibiting the portion of fpawn weighed, the 
number of eggs found in a grain, and the refult of 
examining feveral varieties of the fame fpecies of 
Fifhes of different v/eights, which may be found in 
the Philofophical Tranfaftions, Vol. LVII. 
Fifnes. 
Weight. 
Weight of 
Spawn. 
Fecundity. 
Tim 
Q/. 
Dr. 
Grains. 
Eggs. 
Cnrp - - 
25 
8 
2571 
20^ log 
April 
4. 
Codfifa - 
12540 
3686760 
Dec. 
23- 
Flounder 
-4 
4 
2200 
1357400 
Mar. 
14. 
Herring - 
5 
10 
480 
36960 
oa. 
25. 
Lobfter - 
36 
0 
1671 
21699 
Aug. 
1 1. 
Maci.rel 
18 
0 
546681 
June 
18. 
Perch - - 
8 
9 
28323 
April 
April 
May 
5- 
Pike - .- 
56 
4 
5 1 OCv 
49304 
25. 
Prawn 
(127 
gr-) 
5806 
12. 
Pvo.ich - 
10 
6i 
361 
81586 
May 
Shrimp - 
(39 
7 
H9l 
542! 
6807 
May 
3- 
Smelt - - 
2 
0 
38278 
Feb. 
21. 
Soal - - 
14 
8 
100362 
June 
13- 
Tench - 
40 
0 
383252 
May 
20. 
With refpeft to the generation of Fifhes, the 
general opinion is, that the female depofits her 
fpawn or eggS; and that after this, the male ejefts 
the fperm or femen on it as it lies in the water, 
by 
