326 FIRST FORMS OF VEGETATION. 
the ground, than when he leaves the chance of a 
crop to the scattering self-sown wheat of the pre- 
vious autumn. Indeed, the closest and most pro- 
longed observations, and the most carefully-con- 
ducted experiments—and some of them, especially 
those of Dr. Bastian, have been conducted with 
consummate skill and patience,—have not led to 
the proof of a single instance of spontaneous 
generation, even of one of the simplest of all living 
things ; but, on the contrary, they all, in my judg- 
ment, lead farther and farther from, or entirely 
disprove it. I believe, from the results already 
obtained, that if due care be taken to get quit of 
the ova of animals, and the seeds of minute vege- 
tables from any fluid or other suitable matrix, and 
at the same time carefully to exclude the further 
entrance of them through the admitted air, no 
traces of animal or vegetable life will appear. 
The presence of mould in such an apparently 
inexplicable place as the interior of a large cheese, 
is owing to the exposure of the curd to the air 
when the cheese was being made, and the conse- 
quent deposition upon it of the minute germs of 
fungi floating around, which afterwards developed 
themselves when the curd thus impregnated 
formed the inside of the cheese. It is well known 
that the exposure of curd for a single day to the 
atmosphere will have the effect of producing 
