Final answer:
In the process of spermatogenesis, the cells that develop from mitosis to the formation of mature sperm are known as germ cells, starting as spermatogonia and ending as spermatozoa after various stages.
Step-by-step explanation:
The cell at each stage of sperm development, from mitosis to spermatogenesis, is called a germ cell. The least mature of these cells are the spermatogonia, which are the stem cells of the testis. These spermatogonia undergo mitosis to produce primary spermatocytes, which then divide through meiosis I to form secondary spermatocytes. The secondary spermatocytes undergo meiosis II to become spermatids. Ultimately, spermatids go through a process of transformation called spermiogenesis to become mature sperm cells, or spermatozoa.