4 
the greater ¢, and fo on to the greatet fi I 
have prepared by artin this manner the diGin@ 
little fhells which I here exhibit as gradually 
augmented, And that the method whereby 
this increafe is performed by nature may be 
conceived, I fhall now defcribe and explain how 
this habitation of the Snail is increafed and 
augmented. : 4 
in this {pecies of Snails, I could never dif- 
cover the rudiment of the fhell in the egg it- 
{elf ; but by obferving other kinds I have found 
that the little egg laid by them produced always 
a very {mall but perfect Snail ; and any perfon 
may know, from reafon, that it mutt happen 
thus, fince the Snail’s mufcles would not be 
otherwife ftrengthened by any infertion, which 
no body in his {enfes would even have thought; 
but I follow experience, as the only guide in 
this cafe. In other Snails I have often, through 
the outward fhell, feen the little Snail lying in 
the egg, and moving very diftinétly, before it 
came out, which I have been fo happy asto fhew 
to the illuftrious Van Beuningen, our ambafla- 
dor andconful. One remarkable thing is, that 
as {oon as the Snail is come out of the egg, it is 
perceived to be fo large, that it feems wonder- 
ful how it could lie and mave, fo prefled and 
wrapped up, in that elliptic and narrow cavity 
of the egg-fhell. 
Again, fince the water Snails themfelves 
likewife move in the egg for fome days be- 
fore they come out of it, hence one is in- 
clined to conjecture, that the young Snail does 
not leave .the fhell of its egg before it has 
arrived at a certain degree of growth; at which, 
having its little fhell fufficiently hardened, it is 
in a condition to creep out of the egg, and to 
increafe its flefh and bone, or hard covering, 
with the food it receives. This may likewife 
be feen in other animals, which bring with 
them into the world flefh and bones out of 
the uterus, and only perfect them infenfibly, 
by the ufe of their fucceeding food. By this 
means, the Snail’s fhell is nourifhed, as well 
as its fofter parts; though the former is done 
in fuch a manner, as to lead one to think that 
it is differs in fome meafure ‘from the latter. 
It is befides this worthy of notice, that 
the fhell of the Snail has its particular peri- 
ofteum, by which it is covered and inclofed. 
And the fame may be obferved outwardly 
about the horns of ftags, for thofe are like- 
wife inclofed in a peculiar coat, which they 
rub off againft the trees, and in procefs of 
time wear away, that is, after the horns have 
acquired their full ftiffnefs, and the skin that 
furrounds them is no more nourifhed. I have 
found this membrane fo {trong and tough in 
the thells of fome Snails, that it would not 
yield to aqua fortis; but the fhell itfelf, rather 
than the periofteum, was corroded thereby. 
This membrane is likewife very confiderable 
in the fhells of fea Mufcles, for to this the 
Mutcles faften thofe filaments by which they 
hang. together, and fix themfelves fo as 
to prevent their being carried away with the 
The BO.OK of N.AUR Ee je, 
tide. The filament I {peak of iffues from 
their body, and is very broad in the forepart, 
almoft like a piece of a leather, wherewith 
fome perfons draw on their fhoes; and by the 
affiftance of this, the Mufcles are not only 
joined to each other, but likewife cling firmly 
to rocks,wood, ftones, fea-weeds, or any thing 
that is near them. Thofe filaments in other 
kinds of Mufcles, as in the Pianna Marina, 
are called Byflus, and are that matter, of 
which, as of filk, that kind of very fine 
linnen ufed to be made, which, according to 
Rondeletius, was called Byffus, and in which 
the rich man mentioned in {cripture was 
clothed. . 
In the Snail whereof I here {peak, the 
membrane before-mentioned is pretty ftrong, 
and it is vifible every where in all the notches 
of the fhell, and their interftices, Tab. IV. fig. 
11.5. In other thells of the fame {pecies, I 
have fometimes found it worn out, by the. 
creatures frequent creeping through ftony pla- 
ces ; but it is always confpicuous near the 
aperture out of which the Snail creeps. If 
thofe who delight in natural curiofities, or 
have mufeums, find a fhell {tripped of this 
invefting membrane, they conclude that it 
was rolled in the fea long after the death CE 
the creature originally contained in it. 
I have fometimes obferved that the Snail, 
being about to inlarge its habitation, firft 
cleared away this periofteum with its little 
teeth, nay, that it bit off fome {mall pieces 
therefrom, and fwallowed them; however, I 
have obferved alfo, at other times, that the 
Snail cleaned the edge or margin of its thell 
with its teeth, if it was covered with films, 
and that the Snail happened to reft for any 
confiderable time. I have likewife often 
found that the Snail, when it remains quiet 
for any time, forms films of that kind, and 
befprinkles them with a calcarious matter, and 
then thofe films will ferment with vinegar, as 
well as the fhell itfelf, when worn or rubbed 
in the duft. And indeed all thefe experi- 
ments evidently demonftrate that this habita- 
tion is the real skin, or rather the hard or 
{tony bone of the Snail, which covers it on 
the outfide. 
But if this {tony fhell be accurately exa- 
mined, it appears to confift of numerous f{mall, 
tranfparent, and as it were membranaceous 
coats, which have infenfibly petrified, or 
affumed the nature of ftone; as may likewife 
be obferved in Craw-fith immediately after 
they have caft their fhells, and in the bony 
fkulls of men, which are at firft only thin 
membranes, but are afterwards turned by de- 
grees into bone. Thefe membranes are at firft 
like water, and afterwards grow folid and in- 
creafe, when many fibrous and angular parti- 
cles grow by degrees under them, as may be 
feen moft evidently in the heads of abortive 
children. The fame things may be obferved 
in the Snail’s fhell, if it be lightly calcined, 
and then put under the microfcope. " 
g 
