Basically, he writes that mothers don't need to talk to their daughters. The girls can read all they need to know about it in the Bible.
Here is the full text of his remark:
You can read the whole symposium, which begins with the following: "I look upon the ignorance (adorned by the poetical name of innocence) in which young girls are kept as to the moral and physical conditions of marriage and conjugal life, as proof of the resolution on the part of man, by all the means in his power, to keep girls and women in an inferior position. Knowledge of things, individuals, and conditions of life, is freedom for every living being," here.
