394 PRINCIPLES OF BOTANY, ETC. 
To give am accurate account of all of theni, 
would be transgressing the bounds of our present 
researches ; it will suffice to mention only the chief 
of them. ‘Some of the oldest philosophers thought; 
that an accidental commixtion of solid and liquid 
parts was sufiicient to form, according to ¢tircum- 
stances, animals or plants. This was called Gene- 
ratio aequivoca. Others imagined, that the small ani- 
mals which were observed in the semen, (animalcula 
spermatica), go into the ovaries of the mother, and 
thus form the future being. Others again, believed 
that in the mother a rudiment of the future animal 
pre-existed, to which the semen of the male im- 
parted lite. ‘This theory was called the pre-forma- 
tion system, or the Systema praeformationis, prede- 
lineationis, or the theory of evolution. ‘Those 
three appellations properly denoted three  differ- 
ent ideas; but in reality they all concur in this 
one point, that all three suppose a pre-existence of 
the future being in the mother. Lastly, philoso- 
phers alleged, that the fecundating fluids both of 
female and male become mixed together, and thus 
give existence to the future animal. ‘This theory 
was styled, Lpigenesis. 
The generatio aequivoca, was suppesed in former 
times chiefly to take place in insects, worms and 
plants, but is now entirely abandoned by all ra- 
tionalmen. Harvey’s principle is now well known, 
omite vivum ex ovo, and we daily find this truth con- 
firmed by new and bold observations, and the im- 
portant conclusions of philosophers. I would in- 
deed no longer rest with this old theory, did not 
some 
