Final answer:
The hereditary mechanism that suggests organisms are preformed inside sperm is the homunculus theory. However, this has been disproven by the chromosomal theory of inheritance, which aligns with Mendel's findings on genetic inheritance.
Step-by-step explanation:
The hereditary mechanism that predicts organisms are "preformed" inside sperm is known as the homunculus theory. This concept dates back to the 17th century when Anton von Leeuwenhoek, upon inspecting human sperm under a microscope, believed he saw a tiny, fully formed human, which he called a homunculus. This became synonymous with preformation theory, which posits that all organisms were created in miniature form inside the sperm or, in some versions, the egg.
Later scientific advancements, however, have debunked the homunculus theory. The chromosomal theory of inheritance, largely built upon the work of Gregor Mendel, established that chromosomes are the carriers of genetic material. Observations by Theodor Boveri and Walter Sutton, which showed the importance of chromosomes for embryonic development and their behavior during cell division, support Mendel's findings and demonstrate the mechanism for the passage of genes from parent to offspring.