Final answer:
Spermists believed that a complete, pre-formed miniature human existed within the sperm cell and just needed to grow after conception.
Step-by-step explanation:
What did Spermists Believe?
Spermists were proponents of the preformationist theory of reproduction, which was a widely held belief in the 17th and 18th centuries. They believed that the sperm cell contained a complete, pre-formed miniature version of the future human being, and that this miniature would simply grow to full size once conceived within the womb. This view opposed the ovists' belief, which held that the new individual was pre-formed inside the ovum, and that the sperm merely stimulated the development of the pre-formed being.
The spermists' theory was eventually discredited with the advent of modern genetics and embryology, which demonstrated that both the sperm and the egg contribute genetic material to the offspring, supporting the theory of epigenesis where an organism develops from the successive differentiation of an initially undifferentiated mass. The realization that both parents contribute hereditary information and that development involves a complex process of growth and differentiation led to the decline of spermist (and preformationist) views.