[V. AND REVIVED. 147 
that ‘can merit the name. If we may judge of 
this by-the fenfes, I fay, it:has‘none more than 
the two tremella animals, ‘many infufion animal- 
cula, the prodigious number. and variety of polypi 
vifible by the microfcope and to the naked eye, 
to omit many animals which it would be tedi- 
ous to enumerate. I have never feen the ap- 
pearance of circulation in wheel animals, infufion 
animalcula, in thofe of the tremella, or in 
polypi. Although Baker has obferved the irre- 
gular agitation of a fluid in wheel animals, he 
ingenuoufly avows that he has never perceived 
any trace of real circulation; yet all feed, in- 
creafe, and multiply, as thofe animals which 
have a heart and circulation. Neither are they 
effential to the vital fun@tions of many; for thefe, 
it is enough that there is.a juft equilibrium, a 
correfponding harmony between the fluids and 
the folids. The idea we form of a heart and 
circulation are particular notions derived from a 
definite number of animals, which demonftrate 
the limits of our knowledge and underftanding, 
and would ill apply if we meant to adopt them 
to the immenfity of models framed by nature. 
The wheel animals inhabiting the roofs of 
houfes, towers, and other buildings expofed to 
the inclemency of the weather, fhould be of a 
conttitution calculated to fupport the fevereft ef- 
fects of heat and cold. I put them to the teft. 
K 2 From 
