2 Additional Notes. 



for many successive years, till at length they acquire sexual organs 

 or flowers. 



A third prejudice against the existence of spontaneous vital pro- 

 ductions has been the supposed want of analogy ; this has also arisen 

 from the expectation, that the larger or more complicated animals 

 should be thus produced; which have acquired their present perfec- 

 tion by successive generations during an uncounted series of ages. 

 Add to this, that the want of analogy opposes the credibility of all 

 new discoveries, as of the magnetic needle, and coated electric jar, 

 and Galvanic pile; which should therefore certainly be well weighed 

 and nicely investigated before distinct credence is given them; but 

 then the want of analogy must at length yield to repeated ocular de- 

 monstration. 



Preliminary observations. 



II. Concerning the spontaneous production of the smallest micro- 

 scopic animals it should be first observed, that the power of reproduc- 

 tion distinguishes organic being, whether vegetable or animal, from 

 inanimate nature. The circulation of fluids in vessels may exist in 

 hydraulic machines, but the power of reproduction belongs alone to life. 

 This reproduction of plants and of animals is of two kinds, which may 

 be termed solitary and sexual. The former of these, as in the repro- 

 duction of the buds of trees, and of the bulbs of tulips, and of the 

 polypus, and aphis, appears to be the first or most simple mode of 

 generation, as many of these organic beings afterwards acquire sexual 

 organs, as the flowers of seedling trees, and of seedling tulips, and the 

 autumnal progeny of the aphis. See Phytologia. 



Secondly, it should be observed, that by reproduction organic 

 beings are gradually enlarged and improved; which may perhaps 

 more rapidly and uniformly occur in the simplest modes of animated 

 being; but occasionally also in the more complicated and perfect 

 kinds. Thus the buds of a seedling tree, or the bulbs of seedling 

 tulips, become larger and stronger in the second year than the first, 

 and thus improve till they acquire flowers or sexes; and the aphis, I 



