- coat or membrane. 
The HISTORY. ChAIikNSEC Ts. 
“without any other contents or vifcera, that I 
could difcover. The little animal was alfo 
divided throughout, as it were, into two parts, 
by a very confiderable furrow or fold, Tab. 
“XLVIII. Fig.v. aa. In the upper part there 
ftill remained fome traces of a little yellow fpot, 
that appeared there by fome little openings, 
cracks, or crevices, 6. But on opening after- 
wards the egg, according to the courfe of the 
furrow juft now mentioned, I could difcern 
that, on one fide of the fcetus, this furrow 
reached almoft to the middle of its body, 
where this body was alfo fomewhat convex, 
Fig. vi. 2, in one part; and in the other part, 
to which that furrow equally penetrated, it was 
hollowed into a cavity, 4, which received the 
convexity of the firft. On the oppofite fide of 
the foetus the furrow was not, by a great deal, 
fo deep, ec, fo that it juft looked like a fuper- 
ficial cut on the fkin. The broken fubftance 
of the young Frog’s body, compofed of grains, 
dd, fhewed itfelf in the place where thefe fur- 
rows terminated within. 7 
I afterwards difcovered in a perfect Frog alfo 
this parting or divifion, which I at firft obferved 
by mere chance in the embryos of this animal; 
and this new difcovery procured me great faci- 
lity in accounting for that fudden expanfion 
and elongation of the young Frog’s body, on 
the fourth day, when it explicates or. unfolds 
itfelf. Hence I believe, that one part of the 
unfolded embryo forms the head and thorax of 
the future perfect animal, and the other part 
the abdomen and tail, which grows larger and 
larger by degrees. 
' In the fifth liquor, where I had put fome 
of the eggs, their whites were grown a little 
redifh, and were almoft diffolved; but the en- 
clofed embryos had fhrunk up a little: by 
which means I obtained a fight of a very lim- 
pid humour, that furrounded the young Frogs, 
and was itfelf enclofed in a delicate diftiné 
On examining thefe ap- 
pearances with a great deal of attention, I dif- 
covered, that, on one fide, this membrane 
looked like the allentoies, Fig. viz. a; and I 
could even difcern, in the cavity of it, a little 
white coagulated particle, floating in the en- 
clofed liquor. The furrow, already men- 
tioned, was likewife vifible in the midft of this 
ege, 6; and, on the other fide, the little yellow 
fpot, difcernible in the fcetus, fhewed itfelf 
through the tranfparent membrane which in- 
vetted it, c. This yellow {pot differs in nothing 
from the other parts of the embryo Frog, ex- 
cept that the folds of the body are here larger 
than elfewhere ; and for the fame reafon, in 
proportion as the Frog grows, this yellownefs 
gradually wears away, and changes to black. 
This fecond difcovery gave me room to 
fufpect, that the Frog’s egg might likewife 
leave its amnion and its chorion; and I had 
afterwards the pleafure of difcovering thefe 
membranes, though I cannot take upon me to 
fay, that they can be diftinguifhed one from 
another. But I know for certain, that the 
Frog is wrapped up in a coat or membrane, 
113 
which is very diftinétly confpicuous ; and that 
it floats, moves, and turns itfelf in a moft 
limpid fluid contained in this coat, juft in the 
fame manner as the Chicken does in its colli- 
quamentum, or white. 
This fingular obfervation made me excef- 
fively eager to fearch, to the bottom, thele 
wonderful and furprifing myfteries of Nature. 
I therefore examined this 88 again, touching 
it a little more roughly. By this means the 
allentoies dilated itfelf by degrees, Fig. vir. a, 
as I thus forced into that membrane all the 
liquid contained in the amnion; from which 
however, on removing the little inftrument 
with which I had preffed it, it returned to its 
proper fituation. 
At length, by treating this egg fill more 
roughly, I fucceeded fo far as to make the al- 
lentoies fall off from the Frog; and as, in fo 
doing, I wounded the creature, I could difcern 
its black fluid particles Howing into the allan- 
tois, and at the fame time difturbing the liquor 
of the amnion, which it diftended, thereby 
giving it the fhape of a Pear, Wig. dX. ae 1 
therefore continued this operation, till every 
part of the allentoies was thoroughly expanded 
by the fluid particles of the wounded feetus; 
as may be feen in the tenth figure, done after 
nature, but enlarged. With all this harth 
ufage, I had not as yet broken any of the mem- 
branes. 
I next took a furvey of the Frog’s infide ; 
but I difcovered nothing diftinét enough to de- 
ferve mention. I could only difcern the little 
grains I have already defcribed, and from 
which, as from a congeries of coagulated and 
united globules, this little animal feems to de- 
rive its origin. The menftruums had pro- 
duced in this granulated fubftance a beautiful 
variety of colours, as yellow, white, purple, 
and many others. 
The obfervations already mentioned, had 
thrown fo much light upon the fubject ef my 
prefent inquiries, that the third day after the 
eggs had been difcharged, Tab. XLVIII. (3), 
I could pretty clearly difcern the young Frog 
floating in the liquor of the amnion, and fee 
that it was now gradually expanding itfelf. 
The whole egg alfo was grown much larger, 
by the water and food it had imbibed. The 
albumen that lay next the Frog was fomewhat 
whiter than before; and I even thought that I 
could perceive in this fubftance fome white 
vefiels, which, as I fufpected, might ferve to 
encreafe the white of the egg, and convey it 
to the embryo. We may therefore reafonably 
conclude this has its umbilical veflels, though 
too {mall to be difcerned. I unhappily ne- 
glected this day to put any eggs into the men- 
{truums I had prepared to coagulate them, and 
thereby to obtain an opportunity of looking for 
thefe umbilical veffels. 
On the fourth day 4444, all thefe parti- 
culars were fo vifible, even without the aflitt- 
ance of a microfcope, as not to leave the leaft 
room to Joubt of their exiftence ; efpecially as 
the colliquamentum, or white, and the coats 
ae | inveft- 
