An example of a now-discredited historical conception:
"The two men also spent some time discussing the reproductive habits of crayfish, because Oldenburg was carrying with him a new natural history of the animal by Sir Kenelm Digby, who claimed to have generated the young by distilling the putrid remains of the adults. Huygens found the work 'admirable but I admit that I have trouble believing it'."
Hugh Aldersley-Williams (2020) Dutch Light. Christiaan Huygens and the making of science in Europe. Picador.
This sounds an incredible claim to us today, but spontaneous generation (which did not require any tissue from an adult of the species) of the young of many types of animals was widely accepted over many centuries before a programme of scientific studies slowly discredited the idea.
Dutch Light: Christiaan Huygens and the making of science in Europe
