But compared to egg-making, spermatogenesis is — as I mentioned — a pretty cheap and easy process, biologically.

但和卵子产生相比，精子发生——我提到——一相当便宜和过程，从生物学角度来说。

So the testes have to be outside the body cavity to reach the lower temperature necessary for proper spermatogenesis, or sperm production.

所以睾丸必须在体腔之外，才能达到常精子发生或精子产生所需较低温度。