If Jesus is the seed of the woman (and He is), I believe it is likewise possible that the serpent also has physical seed.
Genesis 3:14 - 15
And the Lord God said unto the serpent, Because thou hast done this, thou art cursed above all cattle, and above every beast of the field; upon thy belly shalt thou go, and dust shalt thou eat all the days of thy life:
And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.