1i4 The BOOK 
invefting the embryo, were likewife greatly in- 
creafed in fize, and the Frog had unfolded and 
difplayed itfelf under a variety of forms; as 
may be feen in the figures I have given, to re- 
prefent them of their natural dimenfions. 
The fame was to be feen on the fifth day, 
and formed a moft furprifing and beautiful ap- 
pearance. I could now alfo difcover by what 
means the chorion and amnion dilate them- 
felves gradually, in the middle of the white. 
The ring alfo, formed by the white veffels of 
the chorion growing round its circumference, 
was now extending itfelf; but with all this, 
no umbilical veffels yet appeared in the colli- 
quamentum of the amnion, though this liquor 
was as tranfparent as chryftal. I could now 
alfo moft diftin@ly difcern the divifion of the 
young Frog into head, thorax, belly, and tail, 
as well as the manner in which it was beauti- 
fully adorned about its thorax, and near its 
head, with fome black fpines, difpofed like a 
border, and highly worth our notice, as I fhall 
hereafter explain. All thefe things may be 
feen in the figure, number 5, Tab. XLVIII. 
I muft here obferve, that I could not now 
any longer difcover the allentoies; but whether 
the fight of it was intercepted by the dilatation 
of the chorion or amnion, or whether it had 
only confifted originally of the folds of thefe 
membranes, or in what other manner this dif- 
ficulty may be explained, I cannot take upon 
me yet todetermine. It was matter of great 
entertainment to me, this day, to fee the em- 
bryo Frogs rolling and tumbling about, almoft 
perpetually, in the furrounding amnion. 
~ On the middle of the fixth day I could per- 
ceive, that fome of the young Frogs had dif- 
engaged themfelves from the chorion and am- 
nion, and deferted the albumen, or white of 
the eggs; whilft others were only preparing to 
break loofe, and others again had not even at- 
tained fo much ftrength and perfection as thefe. 
I obferved alfo, that fome of the eggs had in- | 
creafed in fize, without unfolding themfelves ; 
and thefe, I believe, were fuch as had not been 
impregnated by the male's {perm. IT after- 
wards met with two albumina, or whites, 
which did not now contain, and never had 
contained, any Frogs, though I could difcern 
in them a white fpot; fo that perhaps thefe 
were imperfect eggs, which had dropt from 
the ovary with the reft, and had received 
equally with them their proportion of albumen, 
in paffing through the tubes. Thus did I, in 
this fubject, difcover a great many of Nature’s 
miraculous operations. 
The tenth day (10) I had the pleafure of 
feeing the young Frogs, which had deferted 
their albumina, in an almoft perpetual motion, 
fwimming alternately to this their primitive 
habitation, and then from it again, for the fake 
of reft and food. Thefe Frogs were of the 
form reprefented by the figure, number Jo, 
and they were grown very little larger; but I 
thought it very remarkable, that the little black 
appendages, like borders, before mentioned, 
were greatly increafed in bulk. Thefe {pines, 
of. .N A EU Rese or, 
it is probable, were intended by Nature to 
affift the little animal in {wimming, as well as 
in remaining quiet and repofing itfelf in the 
white. They greatly added to the beauty and 
fingularity of its appearance, according to the 
judgment I had at firft fight formed of them. 
On the 15th J diligently furveyed, through 
the microfcope, the external parts of the young 
Frog, as I have reprefented in two feparate 
figures, of its natural fize, in Fig. xi. and 
in Fig. x11, a, of the fize given by the micro- 
fcope, when laid upon its back. I could now 
moft plainly difcern its divifion into head, tho- 
rax, belly, and tail. The eyes lay on each 
fide of the head, Fig. x11. aa, and were be- 
ginning to project a little, though they ftill 
appeared as if they were thut. On the fore 
part, between the eyes, appeared the animal’s 
wide mouth, 4. A little lower than the head, 
there were fixed to the thorax feveral particles 
in two arrangements, twelve on a fide, very 
much refembling, in form, the little fimbriated 
appendages already mentioned; which I here 
reprefent as rifing from the fides of the body, 
cc. Lobferved, that the little Frog could ex- 
pand thefe particles at pleafure, and draw them 
up towards the abdomen, and afterwards re- 
duce them to their former fituation. The 
divifion of the thorax and abdomen was pretty 
diftinct. In the belly lay an inteftine, which 
{welled beyond the external furface ; and, tho’ 
not completely coiled, formed a great variety 
of windings in its way to the root of the tail, 
where it at laft feemed to terminate, d. The 
ee tail on each fide was fomewhat tran{parent, 
but more opake in the middle, owing to its 
being thicker thereabouts, and to its having 
alfo there a great many cartilaginous parts, 
each furnifhed with its peculiar mufcles for 
moving the tail. I could therefore plainly dif- 
cern, that this cartilaginous and mufcular por- 
tion of the tail, extended to its very extremity, 
J, in the midway between the two membra- 
naceous lateral one. ‘The fkin of this young 
Frog, viewed with the microfcope, looked ex- 
actly as if it was thick fet with black fpots, 
upon a lighter ground, which appeared in their 
interftices. 
On my diffecting this animal, and opening 
its abdomen for the firft time, the inteftine ap- 
peared very confpicuous; but fo delicate, that, 
with the flighteft handling, it diffolved into a 
great many globular particles; as did likewife 
the appendages, which were difpofed with 
great art, like beautifal round {pots, on each 
fide of the thorax. Even the fkin itfelf, when 
handled, fell into particles of the fame form. 
IT could not difcover the ftomach, on account 
of this wonderful tendernefs of the auimal’s 
internal parts. I thought, indeed, I faw the 
heart; but I could not perceive either blood or 
veffels. The contents of the thorax fell alfo 
into little globules, in the fame manner with 
the other parts already taken notice of. The 
eyes exhibited themfelves much more diftinétly 
within the head, than in its outfide. The car- 
tilaginous rudiments of the tail were grown to 
fuch 
