by preformationism. The homunculus theory--famously illustrated by Nicolaas Hartsoeker--proposed that a fully formed miniature human resided within the sperm, requiring only growth within the womb. Competing schools of spermists and ovists disagreed on whether this miniature being resided in the sperm or ovum, but both rejected true organogenesis. The womb was often conceptualized as a passive receptacle.

Although Aristotle (4th century BCE) had earlier proposed a more developmental view than later preformationists, he maintained that