igo Of the frefh Water Polype. 
care muft be taken to choofe thofe which are of a proper 
lize for the polypes to fwallow; they come out of the 
polype’s body without being macerated, the red matter 
which was in their inteftines being only extracted from 
them. 
But this experiment was yet better confirm’d on giv¬ 
ing a polype fome bits of the fkin of a little black, fiat 
fnail, to be met with in great abundance in ditches. The 
matter of this Ikin was foon reduced in the polype’s fto- 
mach to a kind of pap, principally compofed of little 
black fragments, and on examining their motion atten¬ 
tively with the microfcope, were feen to be drove about 
in their ftomach, and to pafs from head to tail, and 
into their arms, even to a thread; and afterwards were 
fent back into the ftomach, and chafed from thence ta 
the extremity of the tail, and were again repelled from 
thence towards its mouth, and into the arms, and fo on 
continually. 
Thefe experiments were feveral times repeated, and 
fucceeded in the fame manner. 
, They are alfo a proof of the polype*s arms being tu¬ 
bular, and that they have an open communication with 
the ftomach. 
The arms of the polype are of the fame colour with 
its body, and an heap of the extravafated grains before 
ipoken of, are of the fame colour alfo; it is therefore 
evident that the colour of the polype depends on the co¬ 
lour of thofe grains which compofe the (kin, (for when 
the polype becomes white, they lofe thole grains) and 
their dependance is upon the nutritive juice, drawn from 
the aliments. 
Thefe grains, for example, become red or black, if the 
polype be fed with a red or black juice; they are more 
or lefs ting’d with thefe different colours, in proportion 
to 
