Why does only one egg, rather than four eggs, develop during oogenesis, given that spermatogenesis results in four sperm formed from one stem cell? why does only one egg, rather than four eggs, develop during oogenesis, given that spermatogenesis results in four sperm formed from one stem cell? once formed, spermatids, but not oocytes, undergo additional rounds of division by mitosis. unequal cytoplasmic division ensures that a fertilized egg has ample nutrients for its journey to the uterus. the egg does not go through the meiotic division processes that the sperm undergo. only one egg can be fertilized at a time.