There are two types: convoluted and straight, convoluted toward the lateral side, and straight as the tubule comes medially to form ducts that will exit the testis.
The seminiferous tubules are formed from primitive sex cords. It is the medullary cords which develop into the seminiferous tubules and the cortical cords regress. The cords were formed from the gonadal ridge.
Seminiferous tubule (right) with sperm (black, tiny, ovoid). H&E stain.
Transverse section through the left side of the scrotum and the left testis. (Semeniferous tubules visible in center, but not labeled.)