. . M i c r o s c o p i c a l E s s a y s .
0 Jp
from whence it is prolonged in the form o f a black line m n n>
which pafles by the axis of the duft e e h , and apparently terminates
itfelf at the beginning of the abdomen k. To this tube,,
near the center of the fwelling g h i, are fixed two fmall tranf-
parent bodies ; that end of thefe which is connefted with the tube
is round, the other end is pointed ; thefe fmall pieces cannot be
difcerned in every pofition of the eel.
We muft now fhew how this duft is to be forced out of the
eel. The body, when comprefled, generally burfts either at the
head or tail, and always at that part which is leaft prefied; hence
when the mafs of fluids contained in the body is forced towards
the anterior part, they meet with a refiftance in palling from the
abdomen to the duft already' defcribed; the abdomen being '
forced by the fluids which are made to aft againft it, burfts at the-
upper, part, and the fluids Itriking againft the neck g h i, force it,,
with all it’s contents, out of the body, through an opening at
the anterior part; on leffening the preffure, the bowel, thus dif-
charged, will float in the water between the two plates of glafs.
Not to enter into a detail of thofe parts which have been fup-
pofed by fome writers to conftitute the heart, &c. o f thefe
minute animalcula, it will be fufficient here to defcribe thofe in
which motion may be difcovered, and to leave the reft to futule-
obfervations on the fubjeft. The parts which may be feen in
motion within thefe minute creatures are, l. the fmall tube, or
duct, from it’s origin at m, to the two appendages t 2. thefe
appendages themfelves ; 3. the remainder of the tube, from the
appendages to the infertion at the ventricule k ; 4. m the fwelling
g k 1. The reft of this duff, from the beginning by the
oefophaoefophagu's
b c, to the fecond fwelling, has no motion. There is
a variety in the motions o f the firffi part o f this duft, fometimes
it dilates and contrafts, at other times it has an ofciilatory motion.
It is difficult to gain a good view o f the appendages, but when
the pofition of the little creature is favorable, they -feein to have
a two-fold motion, by which the pointed ends approach to, and
then feparate from each other, and another by which they move
up and down. The part g k 1 moves backwards and forwards
alternately, the motion of each o f thefe parts is independent of
the reft. Thefe are the principal parts, whofe motion is connected
with the life o f the animal.
The other vifcera that are contained in the body of the eel*
and which may be obferved by the aid of the micrOfcope, are the
veflels which contain the food, thofe which are filled with a tranf-
parent fubftance, and the womb, or ovary. The firft form the
abdomen and inteftines; thefe are filled with a black fub fiance,
which prevents their being properly and clearly diftinguilhed ;
thefe veffels, in their paflfage through the pofterior part of the
body, form an-empty fpace, in which we may perceive that one
fide o f , the animalculum is occupied by the ovary- q q q , which
runs from j to u x ; it is at thefe two extremities of the ovaries
that the eggs begin to be formed, for the largeft eggs are always
to be found in the middle, and the fmalleft at the' ends, as may
be feen at j f and u x.
All the eels which bear eggs- have two protuberances, y y,
formed on the exterior part, near the center of the ovary; it appears
like a tranfparent fèmicircular membrane, but is really a
kind of hernia, or bag, in which one or two eggs may be fome-
3 R 2 - - times