Stages of spermatogenesis
The maturation of germ cells occurs in cell-association stages, each with a unique group of developing cells undergoing spermatogenesis.
In humans, developing stages form irregularly-shaped patches that do not extend completely around the lumen. Thus, any given cross section will contain more than one stage. There are 6 stages in humans and they are not arranged sequentially along the tubule.
In rodents and non-human primates, the stages extend around the entire circumference of the tubule. Thus, individual cross sections contain a single cell-association stage and they are arranged sequentially along the tubule.