Sol had told Nerodia that he would find another way and postponed the decision as the Seed had not even become a Nymph yet, it would need some time or maybe a long time before it develops into a more advanced being.
He was thinking about whether he could influence the Seed's growth so he could modify the end result of its development.
The best-case scenario was he made the male version of a nymph but he also has some alternative way that he could choose to go, he could invent a Nymph cloning or just made the retain the ability to reproduce asexually.
Sol would need the help of Nerodia to do it but he was optimistic with his knowledge of modern science he could at least have some result, he refused to believe that he would fail.
Even though his knowledge of genetic modification was not anywhere near good enough, he would try his best, although he did not even know whether a Seed or Nymph had DNA, there surely be a spirit equivalent of it.