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reafon of the various Motions the Infett gives its 
Body, thefe others juft defcribed appear for fome 
Space retrograde. 
The Earth from which thefe Worms receive their 
Nourifhment, and which they digeft, is not however 
the only Matter which is admitted into their Bodies ; 
the Air often enters alfo in Bubbles that are very per- 
ceptible. But whereas Fifties have the Air in their 
Bodies at their own Command, and can make ufe of 
it for railing or finking themfelves; our Worms, on 
the contrary, are, in fome meafure, maftered by it : 
As foon as they happen to fwallow a certain Quantity 
of it, it is hardly poftible for them, notwithstanding 
their continual Efforts, to get to the Bottom of the 
Water; and they are forced to remain on the Sur- 
face, till they have got it all out again. I have feen 
fome of thefe Bubbles alternately driven towards the 
Anus , and repelled towards the Head, for feveraL 
Minutes together. 
Thefe are the principal Particulars, which the Mi- 
crofcope enables us to difeover in the Stru&ure of 
thefe Worms; which being once known to a certain 
Degree, we fhall, without doubt, the more admire 
the Wonders of their Reproductions. 
II. I mentioned above, that I had divided one of 
thefe Worms in two. I put thefe Two Halves into 
a fort of Glafs Cup, filled only with Water, and 
attentively watched them during the following Days. 
I obferved that the Firft Moiety, that which had kept 
its Head, moved as ufual; but what feemed to me 
far more remarkable, was, that the other Moiety, that 
had no Head, moved almoft as if it had one ; it went 
forwards, refting itfelf upon the anteriour Extremity 
