 At least three variants of the theory of pre-existence can be distinguished. Two of these assumed the pre-existence of forms in miniature, either encased in the ovaries of the female (Ovism), the original version, or after the discovery of spermatozoa by Anton van Leeuwenhoek in 1677, in the testes of the male (Vermism). These two versions of “preformationism” generally became the main options one finds expressed in the professional medical and gynecological literature of the 1670–1740 period. A third alternative, which had few followers in the seventeenth and early eighteenth century, but which became particularly popular by the 1770s, was the theory of pre-formed “germs”, given its first clear statement by Claude Perrault (1608–80). This Perrault theory, which closely resembled the Augustinian account, held that the first primordia of organisms were formed at the original creation as seeds dispersed in the soil, from which they were taken in with food. Under the proper conditions and within the correct organisms, these “germs” became implanted in the ovaries from which they then developed in response to fertilization. In all three accounts, the act of fertilization provided the occasion, and not the cause, of the development of organisms in time.