Final answer:
Descent of the testes into the scrotum normally occurs near the end of the seventh month of fetal development, essential for temperature regulation required for sperm viability.
Step-by-step explanation:
The descent of the testes into the scrotum normally occurs near the end of the seventh month of fetal development. During this time, each testis moves through the abdominal musculature and descends into the scrotal cavity—this process is known as the descent of the testis. This descent is crucial for maintaining the correct temperature required for sperm viability, which is about 2°C lower than body temperature. Should the testes not descend by birth, a condition known as cryptorchidism occurs, which can lead to reduced fertility due to the higher internal body temperatures.