ICHT.H YOLOG Y. 
Teems to have fcarcely any bounds put to its growth,' 
continues to live, is not afcertaineci, Some fpecies of the 
German carp have been known to live two or three hun¬ 
dred years ; thole fpecies, however, with which we are 
belt acquainted, feem not to enjoy fo great a degree of 
longevity. The faltnon takes only fix years to reach its 
full fize; if we allow four or five times that fpace for the 
period of its life, it will not exceed thirty years. But 
Leeuwenhoek is of opinion, that the growth of fifties is 
not fubjeft to the fame rule as that of other animals: “ I 
am perfuaded (fays he), that all fifties which have a con- 
itant fupply of food do daily increafe in fize, and this 
■without ever ceafing to grow j fo that any real definite fize 
cannot be aftigned to them, as it can to terreftrial ani¬ 
mals, fome of which arrive fooner, and others later, to 
their full and perfeft llature, which they never afterwards 
exceed, although they continue to live many years. The 
reafon of which, I am convinced, is this: that terreftrial 
animals continue growing as long as their nutritive juices 
have force fufiicient to protrude or thruft themfelves 
through the cavities of the bones, and fo to increafe the 
fize of them, as well in length as in thicknefs; but, when 
•the bones of thele animals, by being expofed to the air, are 
become fo rigid and hard, that they, cannot be any more dif- 
tended, their farther growth mult neceflarily ceafe, and any 
frelli fupplies of nutritive juices can only tend to increafe 
the animal's fatnefs. Now the bones of fifties are for the 
molt part deftitute of marrow, and they cannot be ren¬ 
dered rigid by expofure to the air, conl'equently the very 
fmall tubuli or pipes of which they are compofed, are ex¬ 
ceedingly foft in comparifon with thofe of other animals. 
All which confidered, there feems no reafon to exilt, why 
the bones of fifties ftiould not continue always growing fo 
long as the animals do not want for food. In the lakes 
with us, where are many fiflieries, pike have been caught 
of the length of 56 inches, and 36 or 38 pounds weight. 
Perch alfo 28 inches long ; and who can tell to what 
fize thefe fifties might arrived, if they could have longer 
efcaped the nets ?” 
Different methods have been devifed for afcertaining 
the age of fifties, fome of which will, perhaps, pretty ac¬ 
curately determine this matter. The ingenious Mr. Hid- 
doftroam, a SiVede, attempted to compute their ages by 
the number of concentric circles obferved in a tranfverle 
feftion of the vertebree of the back ; and it was found, that 
each circle, like that in the feftion of a tree, correfponds 
to a year of the animal’s life. In confirmation of this faff, 
experiments have been made on different individuals of 
various fizes, but of the fame age, whole concentric cir¬ 
cles have always been of an equal number; whereas a 
young fifli differs front an older one of the fame fpecies, 
by having a fmaller number of thefe circles. By this me¬ 
thod of computation, feveral fifli were found from fifteen 
to twenty years, but none gave indications of a greater age. 
Another method of computing the age of fillies, pracfiled 
by the comte de Button, is by numbering the concentric 
circles upon their fcales ; but, as this requires a more mi¬ 
nute examination, it is, of confequence, liable to greater 
uncertainty. Oil examining the ficale of a fifli through a 
microfcope, it exhibits a number of circles, one within 
another, reiembling thofe in the vertebrae of the back ; and, 
like them, every circle reprefents a year of the fifti’s life. 
A fcale of a carp, thus examined, announced the animal 
to be no lets than a hundred years ; a longevity lei's in¬ 
credible, becaufe confirmed by the teftimony of feveral 
different authors, fome of whom have afferted, that this 
fid) lives thrice that period. 
M. Leeuwenhoek, the Dutch naturalift, has fome very 
curious particulars relating to the fcales of fifties, and the 
mode of difcovering the age of fifties by an'examination 
of them ; and we fhall avail ourfelves of his tranftator’s 
permiftion, not only to tranfcribe a part of the matter re- 
fpefting that fubjeft, but to copy the accompanying 
figures in illuftration. M. Leeuwenhoek began with the 
fcales of the eel, Murania ansruilla, for the followin* 
fealons : 
“ It is the opinion of the Jews that they are forbidden, 
by their law to ule the eel as food, becaufe that fifli is faid 
to be without fcales ; and in the book of Deuteronomy, 
chap. xiv. ver. 10, it is written, Whatfoever hath not fine 
andfcales, ye may not eat, it is unclean unto, you ; and in Le¬ 
viticus, xi. iz, are t-hefe words, (which they apply to the 
fame fpecies of fifli;) Whatfoever hath no fins nor fcales in the 
waters, that frail he an abomination unto you. But, when I 
examined this kind of fifli by the microfcope, after I had 
cleared away that vifccus or fiimy matter which -adheres 
to them, I found their (kins to be as'completely covered 
with fcales as thofe of any other river-fifli, which fcales 
(though very fmall and thin) lie as clofe together and are 
placed one on another in as regular order as can be ob¬ 
ferved in any other fifli whatever, whether of.frefh or fait 
water. Moreover, this fpecies of fifli is provided with 
fins equally as ot hers, namely, one at the head ; and one 
above, and another below--, the tail. And, becaufe I ap¬ 
prehend that this difcovery of mine is new, at lealt to 
perfons of the Jewifti nation, (for to this day they deem, 
this delicate fifn to be unclean, and hold it as an abomi¬ 
nation to them,) I determined to give a figure of one of 
thefe fcales, (taken from the belly of the fifli, where they 
are the fmalleft,) as it appeared through the microfcope. 
Plate II. fig. 1, ABCDj exhibits this fcale; it was taken 
from the belly of a large eel, .which, next the head, was of 
the thicknefs of feven fingers or thereabouts : 011 the back 
and fides of this fifli the fcales are larger. The greateit 
part of this fcale, ADC, was covered by two others. 
The part B was placed towards the tail, and in this poli- 
tion were all the fcales; they were all.principally compofed 
of a kind of globules or little balls, which were very 
tranfparent, though fome more than others ; again, fome 
had in them a dark fpot. Thefe opaque globules, lying 
in rows contiguous to each other, produced the appear¬ 
ance of divers circles or rings on the face of the fcaje. 
And, although I did not oblerve thefe fcales to be ex¬ 
actly alike, yet the circles or rings feemed to me to be of 
the fame number in all of them, whence 1 was led to 
conclude, that the fcale had been every year augmented 
by the addition of one circle, and conlequently, that, as 
there were feven circles in this fcale, this eel was proba¬ 
bly leven years old. Thefe circles are marked in fig. 1 by 
the letters EFGHIKL, and at X the fcale is reprefented 
of the fame fize as it appeared to the naked eye. 
' :t Having examined the fcales on the body of a very 
large eel, I perceived that thofe on the back and belly of 
the fifli were placed in regular and even courles behind 
each other, but that thofe between the back and the belly 
were many of them laid obliquely, fome towards the belly 
and others towards the back, but all fo dilpofed as to co¬ 
ver the fkin exaftly in every part. After this, I ex¬ 
amined the matter or fubftance with which thefe fcales are 
covered, which, as well as the fcales, has been generally 
deemed nothing more than flivne, and is by molt perfons 
thought to be an excrementitious matter adhering to this 
fpecies of fifn ; but I am now convinced by experience, 
and the cleared ocular demonftration, that this l’uppcfed 
llirne does nct-colleft on the animal’s body from without, 
but is really part of the body itfelf; forafmuch as this 
fubftance, although it appears to the naked eye, and very 
often through the microfcope, no ctherwife than like a 
cryftalline or pellucid humour or fubftance, yet in faft it 
is no other than a congeries or colleftion of veins or vef- 
fels, which in their exquifite finenefs or fiendernefs do al- 
moft exceed belief, fpreading themfelves one among ano¬ 
ther in fuch an incomprehenfible and immenfe number of 
branches, that I could not contemplate them' without the 
greateit admiration. Indeed, many were fo thin and 
(lender, that I could not difeover them without the molt 
careful attention; and I thought it probable that there 
might be others Itill more minute, fo as entirely to elcape 
