ANIMAL REPRODUCTIONS. 245 
fufficient materials to explain it. Was the orga- 
mic ftru@ture of the reproducing fnails very differ- 
-ent from thofe that do‘not reproduce, fome rea- 
fon might be affigned for it; or, ‘to {peak more 
philofophically, was there any difparity between 
them. ‘However, no fuch thing was found, at leaft 
by me, with.any certainty, among the'various fpe- 
cies of {nails that either fucceeded or did-not fuc- 
-ceed in reproducing. 
This uniformity of organization in {nails fpecifi- 
ally different, which at the fame produces oppo- 
fite refults, as reproducing and not reproducing, 
is a ufeful leffon that we cannot avail ourfelves of 
analogy in reafoning from one {pecies to another ; 
‘but that truth may be attained, we are under the 
neceflity of undertaking as many experiments as 
there are animals fpecifically different ; and the 
force of this conclufion, fo humiliating to us, is 
more plain and evident, by throwing a traffient 
glance on the various animals which naturalifts 
» have at different times difcovered to be endowed 
with a reproductive virtue. 
~ When the immortal Trembley firft difplayed 
the prodigies of the polypus to the philofophical 
avorld, it was thought that the very fimple ftruc- 
ture of the animal chieiiy contributed to effeé& 
them. Indeed, the polypus being deftitute of a 
heart, veins, and arteries, and, confequently, of 
the real circulation of fluids; neither brain, fpi- 
Q 3 nal 
