Atreya, the foremost or leading among the sages, said to devoted Agnivesha. [Process of ejaculation and causes of vitiation of shukra (defects in semen and sperms)] As the semen (shukra) gets ejaculated as a result of excitement and it is the sign of masculinity.
The reason behind calling it as seed will be explained by me . The seed as an effect of delighted coitus, has been described as shukra,it is the male characteristic known as semen.
यथा बीजमकालाम्बुकृमिकीटाग्निदूषितम् | न विरोहति सन्दुष्टं तथा शुक्रं शरीरिणाम् ||१३४||
As the (plant) seed at inappropriate time, affected by unseasonal rains, worms, pests & fire does not grow out, in the same way the semen (does not grow up) in human body.