 The remainder of this discussion will focus on the general causal theory of animal generation developed in the first half of GA  II.[12]  In the closing chapters of book I, Aristotle argues that both the male and female contributions are formed from a ‘useful residue’ of blood by a concocting process, the male’s being more fully concocted than the female’s. From this point on the male’s contribution is typically termed gonê (semen), and the female’s katamenia (menses). Aristotle is not entirely consistent, however: occasionally he uses the generic term sperma for the male contribution and explicitly contrasts it with katamenia (727a27–30); while at other times he refers to katamenia as a sort of sperma (728a26–29).