[ 592 ] 
the microfcope j and I have even made my obferva- 
tions without its afliflance. 
A Defcription of the Worms which form the Sponges. 
The worms I found in thefe kinds of fponges are 
about one-third of a line thick, and two or three 
lines in length. They are fo tranfparent, that one 
may difcern their vifcera thro’ their coverings and 
fubftance : the blood may be feen to circulate, and 
all their parts to add. They have a conic figure, 
with a fmall black head furnifhed with two pincers: 
the other extremity is almoft f'quate, and much larger 
than the head. Upon the back may be feen two 
white ftreaks or fillets, as if they contained the chyle: 
thefe two canals are parallel to each other from the 
head to the other extremity, where they come to- 
gether. In the middle, where the belly and *vifcera 
ought to be placed, a blackifh matter is perceivable, 
which has a kind of circulation : fometimes it fills all 
the body of the worm, fometimes it gathers towards 
the head, or at the other end, and fometimes it follows 
the motion of the animal. Tins vermicular motion 
or progrefhon begins at the pofterior extremity, and 
ends at the head, which is pufhed, and confcquently 
advances forward. I kept thefe worms alive out of 
the fponge, quite detached from it, more than an 
hour, having examined them thoroughly with a 
middling magnifier ; for a great magnifier would be 
the grave of the infetft. 
I was furprifed, after having finifhed my obferva- 
tions, when I put them near a piece of the frefh 
fponge, where the nefts were moift, and from which 
I had 
