84 
manner obferved in the viviparous Snail ; and 
if thefe Worms be diffected, a great many 
{maller ones, with thick little heads iffue from 
them, which will likewife {wim with very great 
velocity, and they alfo are ftronger in their life 
and motion, than thofe which I have defcribed 
_in the account of the viviparous Snail. 
Thefe Worms likewife creep with very great 
{wiftnefs ; firft ftretching their head forward, 
and then, with great force, drawing the reft of 
the body after it. Their greateft {trength is 
in their mouth, which may probably have a 
kind of feet, as I have feen in other little crea- 
tures, and fhall hereafter defcribe and exhibit 
in figures. Thefe Worms are much fmaller 
in this than in the wonderful Snail. When I 
was certain of this fact of the Worms, from 
obfervation, I kept fome thoufands of them in 
the water, wherein I kept thefe Snails enclofed 
in a large glafs veffel, and I faw that they 
moved {wiftly. The little part of this Snail 
which contains thefe Worms in the upper part 
of its membrane, is on the infide of a bright 
yellow colour; and, in my opinion, may pro- 
bably be accounted analogous to the purple- 
bearing bag in other creatures of this kind; but 
this I fhall not affirm certainly. 
This Snail agrees with the common water 
Snails with refpect to the external ftructure of 
the mouth and teeth. It wants an operculum 
or cover, but as to moft of the vifcera it is 
likewife like them. Its ftomach is formed in 
the fame manner as that of the Hen. The 
brain is fituated alike, though there is “fome 
difference in the nerves. ‘The heart is placed 
in the left fide of the body. But there is one 
peculiar thing in this, which is, that the liver 
confifting of glandules, is not protended to the 
extreme cavity of the fhell: Ihave found there 
a {mall part which was filled or crammed as it 
were with myriads of the thick-headed little 
‘Worms before defcribed. The chain-like little 
part follows next, behind which is placed ano- 
ther glandulous purple-coloured {mall part, and 
after this again is feen another yellowith little 
The BOOK of NATURE: of; 
part near the uterus, which is of the like frucz 
ture with that in the water Snail, and Opens 
with three tubes into the hinder part of the 
neck. The penis is formed in the fame mariner 
as in the common water Snail, nor has it any 
thing peculiar in it, only that where it is ex- 
tended out of the body, three fmall folded 
parts are feen, the middle whereof is very 
beautiful, and is, in fome medfure like a 
mufhroom, fupported by a fmall foot, and di- 
vided on one fide. 
The fmall flattened Snail. 
This Snail is in moft refpeéts like the for- 
mer, nor does it differ from it, except that its 
fhell is on each fide almoft fmooth, and is con- 
cave, and adorned with a {mall kind of mar- 
gin, Tab. X. fig. v. a, by the addition of 
which it happens that the furrows or little 
ribs in the furface of the fhell are bent ina 
different manner. It is feldom found larger © 
than it is here reprefented. There is alfo fome 
flight difference in the external part of the 
body. The horns are fleth-coloured, though 
the body itfelf is blackifth. The fhell of this 
Snail put in the fun is almoft all tranfparent, but 
particularly in its internal windings, which are 
on every fide ftained with purple. The punc- 
tum faliens, or beating heart, is obferved to be 
deeply tinctured with the like colour. But if the 
body of this Snail, after it has crept out of the 
fkin or fhell, be pierced with a {mall needle, and 
the needle afterwards extracted, it draws back 
its body very deep into the fhell; and then it 
is obferved, that a juice of a purple colour in- 
fenfibly diftils out of the wound. This I take 
to be a certain fign that this little creature has 
purple blood. Whether this fame thing holds 
in the foregoing Snail, is yet to be difcovered 
as alfo in a {maller one; the thell of which is 
likewife probably fo thin as to be tranfparent. 
This and the former Snail are found in the 
ditches in Holland, as well as near the high- 
ways and in pafture grounds, 
Of frefb-water Mufcles, found in the rivers in Holland. 
YON the river Vecht above Amfterdam, and 
in other rivers, is frequently found a fpecies 
of Mufcles, which are indeed buried in the 
clay and mud next to the banks, but they lie 
free and difengaged, and ftretch out their fharp- 
pointed part. When the bottoms of the Vecht 
or neighbouring ditches are cleaned, thefe muf- 
cles are found in great numbers. I difcovered 
three fpecies of them ; a larger fort with thin 
and broad fhells; a {maller more oblong, and 
with thicker fhells; and a very large ‘kind, 
which is of a fomewhat different texture. 
I only examined the middle fpecies of thefe, 
that is, thofe which are moft common. Thefe 
do not open themfelves much, they only make 
the two wings or lips of their bodies to fwell a 
little out of the fhell, and by this means they can 
fill themfelves with the river water. Befides, 
they emit out of the fhell fome {mall ruddy api- 
cull, or {mall points, with fharp extremities; and, 
as thofe are on the hinder part covered with a 
blackith fubftance, they refemble fo many fharp 
and black little {pines, made like the papillz that 
are obferved on the furface of a Cow’s tongue. 
I had intended to complete the whole ana- 
tomy of thefe Mufcles; but when I opened 
two of them, all the parts that I found in them 
were fo ftrange, and fo much unknown to me, 
that I defifted from my purpofe for that time. 
For, as I had never before accurately diffected 
any fpecies of Mufcles, I faw that it would 
have taken up a very long time to have finifhed 
this bufinefs, and I was then deeply engaged 
in other matters. I therefore referve this work 
for 
