Sperm Donation

Q: Is it permissible to donate to a sperm bank?
A: The problem with this is that the child will not know who his father is and he may then marry one of his relatives. Our Sages in the Gemara obviously did not discuss this issue but they spoke about something similar: It is forbidden for a man to marry different women in different countries (after divorces) out of a fear that his children may marry one another. It is therefore forbidden to donate to a sperm bank. When a couple wants to have an artificial insemination – which the majority of authorities permit – the solution is that the sperm come from a non-Jew, since then the relation is only through the mother and not the father.