In man, Cryptorchidism is the condition when

The correct answer is testes do not descent into the scrotum.

What is Cryptorchidism?
Cryptorchidism is a medical condition in humans and other mammals where one or both of the testes fail to descend from the abdominal cavity into the scrotum during fetal development.

Developmental Background:
During embryonic development, the testes form inside the abdominal cavity near the kidneys. As the fetus grows, the testes gradually migrate downward and pass through the inguinal canal to reach their permanent position in the scrotum before birth. This descent is critical because the scrotum maintains a temperature that is 2 to 3 degrees Celsius lower than the normal core body temperature, which is essential for normal sperm production (spermatogenesis).

Analysis of Options:
- testis degenerates in the scrotum: Incorrect. The testes do not degenerate in the scrotum; rather, they fail to reach the scrotum.
- testis enlarges in the scrotum: Incorrect. This describes conditions like orchitis or testicular hypertrophy, not cryptorchidism.
- there are two testes in each scrotum: Incorrect. A normal scrotum contains one testis on each side (two in total in the scrotal sac).
- testes do not descent into the scrotum: Correct. This is the definition of cryptorchidism.