The Sex Organs - The Male Sex Organs

The Internal Sex Organs: The Production of Sperm

2. The Second Step
The primary spermatocyte does not duplicate itself the way all other cells do, but divides in a unique way: It splits in half, as it were, allotting 22 chromosomes plus 1 X chromosome to one of the new cells, and 22 chromosomes plus 1 Y chromosome to the other. The two new cells are called secondary spermatocytes, and each of them contains only half as many chromosomes (23) as all other body cells.