Answer:
Endospores
Explanation:
Endospores are hardy defensive structures formed by bacteria to survive harsh conditions.
Tyndall tried to replicate Pasteur's experiment however, even after boiling the broth sometimes the S necked flask gave rise to microorganisms.
This is because, the bacteria produces endospores which are thermostable hence they were not destroyed during boiling.
They will later on grew on the broth when the conditions became favorable.
