PIS 
A few species, indeed, as the eel, blenny, 
&c. are viviparous ; but by far the greater 
number are produced from eggs. These 
last compose the roe, ovaries of the females, 
which lie along the abdomen. The milt 
ef the males is disposed along the back- 
bone, in one or two bags, and consists of a 
whitish glandular substance, which secretes 
the spermatic fluid. Though -the history 
of the generation of fishes be still involved 
in considerable obscurity, it seems to be 
ascertained, that no sexual union takes 
place among the oviparous kinds, and that 
the eggs are fructified after exclusion. They 
are of a spherical form, and consist of a 
yolk, a white part, and a bright crescent- 
like spot, or germ. The yolk, which is 
usually surrounded by the white, is round, 
and not placed in the middle, but towards 
one of the sides; and the clear spot, or 
embryo, is situated between the yolk and 
the white. 
In this spot there is observable, on the 
day after fecundation, a moveable point, of 
a somewhat dull appearance. On the third 
day, it assumes the appearance of a thickish 
mass, detached on one side, and on the 
otlier strongly adhering to the yolk, and 
presenting the contour of the heart, which 
at this period receives an increase of mo- 
tion, while the disengaged extremity, which 
forms the rudiments of the tail, is perceived 
to move at intervals. On the fourth day, 
the pulsations of the heart, and the move- 
ments of the whole body occur in quicker 
succession. On the fifth, the circulation of 
the humours in the vessels may be discern- 
ed, when the fish is in a particular position. 
1 On the sixth, the back-bone may be dis- 
tinctly recognised. On the seventh, two 
black points, which are the eyes, and the 
whole form of the animal, are visible to the 
naked eye. Altliough the yolk gradually 
diminishes as the embryo enlarges, the in- 
cluded animal cannot yet stretch itself at 
length, but makes a curve with its tail. Its 
motions are then so brisk, that when it turns 
its body, the yolk turns with it; and these 
motions become more and more frequent, 
as the moment of birth, which happens 
between the seventli and ninth day, ap- 
proaches. By repeated strokes of the tail, 
the covering of the egg at length gives way, 
and the fish comes forth, first by the tail, 
redoubling its efforts, till it detach its head ; 
and then it moves nimbly, and at liberty, 
in its new element. 
Fishes have different seasons for deposit- 
ing their spawn. Some, which live in the 
PIS 
depths of the ocean, are said to choose the 
winter months ; but, in general, those with 
which we are acquainted choose the hottest 
months in summer, and prefer such water 
as is somewhat tepified by the beams of 
the sun. They then leave the deepest parts 
of the ocean, which are the coldest, and 
shoal round the coasts, or swim up the 
fresh-water rivers, which are warm as they 
are comparatively shallow, depositing tlieir 
eggs where the sun’s influence can most 
easily reach them, and seeming to take no 
farther charge of their future progeny. 
Of file eggs thus deposited scarcely one in 
a hundred brings forth an animal, as they 
are devoured by all the lesser fry which fre- 
quent the shores, by aquatic birds near 
the margin, and by the larger fish in deep 
water. Still, however, the sea is amply 
supplied with inhabitants: and notwith- 
standing their own rapacity, and that of 
various tribes of fowls, die numbers that 
escape are sufficient to relieve the wants 
of a considerable portion of mankind. In- 
deed, when we consider the fecundity of a 
single fish, the amount will seem astonish- 
ing. If we should be told, for example, 
that a single being could in one season’ 
produce as many of its kind as there are 
inhabitants in England, it would strike us 
with surprise: yet the cod annually spawns 
according to Lewenhoeck, above nine’ 
million of eggs contained in a single roe. 
The flounder is commonly known to pro- 
duce above one million ; and the mackarel 
above five hundred thousand ; a herring of 
a moderate size will yield at least ten tliou- 
sand ; a carp, of fourteen inches in length 
contained, according to Petit, two hundred’ 
and sixty-two thousand two hundred and 
twenty four; and another, sixteen inches 
long, contained three hundred and forty-two 
thousand one hundred and forty-four- a 
perch deposited three hundred and eig’hty 
thousand six hundred and forty; and a 
female sturgeon, seven million six hundred 
and fiftpthree thousand two hundred. 
The viviparous species are by no means 
so fruitful; yet the blenny brings forth 
two or three hundred at a time, all alive 
and playing round the parent together. 
Pisces, in astronomy, the twelfth sign 
or constellation of tlie zodiac! The starsin 
Pisces, in Ptolemy’s catalogue, are thirty- 
eight ; in Tycho’s thirty-three ; and in the 
Britannic catalogue one hundred and nine. 
PISCIDA, in botany, a genus of the 
Diadelphia Decandria class and order. 
Natural order of Papilionaceae, or Legumii 
