Pasteur used swan-necked flasks and a nutrient broth to demonstrate that spontaneous generation of organisms does not occur on Earth. Some students performed a similar experiment using two swan-necked flasks, one containing broth which had been previously boiled and another containing broth which had not been boiled.

Pasteur used swan-necked flasks and a nutrient broth to demonstrate that spontaneous generation of organisms does not occur on Earth. Some students performed a similar experiment using two swan-necked flasks, one containing broth which had been previously boiled and another containing broth which had not been boiled.

The flasks were left in the school laboratory and observed after one week. What is the evidence against the spontaneous generation theory?