The Greek philosopher Aristotle believed that certain animals grew not from sexual reproduction, but spontaneously from inorganic matter.
So with animals, some spring from parent animals according to their kind, whilst others grow spontaneously and not from kindred stock; and of these instances of spontaneous generation some come from putrefying earth or vegetable matter, as is the case with a number of insects, while others are spontaneously generated in the inside of animals out of the secretions of their several organs.
Barnacle geese were thought to form on driftwood, first as an amorphous blob, then forming beaks (which held onto the wood) and protective shells. Once they had formed feathers, they could break free from the wood. Apparently, this belief allowed early Christians to classify waterfowl as "fish" and allow them to be eaten during lent.
Other examples of spontaneous generation were flies (born from rotting meat), bookworms (generated by winds blowing on south-or west-facing libraries), and eels (which either sprung forth from earthworms, or created new eel-forming particles by scraping themselves against rocks.)
Frankly, I think there's a lot of charm in these early attempts at describing the natural world. And before we scoff at these ideas, I think we should consider how future astronomers or physicists might consider our current methods of describing the lesser-known regions of cosmos. Dark matter? Strange quarks? Sure, whatever.
In any case, I feel that I have mastered the science of spontaneous generation. I've taken coffee grounds, and kitchen waste, and sawdust, and I've created black delicious smelling earth. And lots and lots of tiny wriggling red earthworms.
The Grouch Marx hypothesis notwithstanding, everyone knows that earthworms are formed from banana peels!