Page 46, for the uninitiated, is the latest in the long history of "dirty pages" in school science textbooks. It is, in fact, a relatively tame version of the genre, diffidently headed "fertilisation" and carrying a rigorous cross-section diagram of copulation.
But it has proved too much for some teachers in Trinidad and Tobago. While the Government backs the book, church schools are going nuts over its "graphic depiction" of sex.
"But what really seems to have upset them is the suggestion in the text that sex is pleasurable," says joint author James Williams, of the University of Sussex Institute of Education.
He therefore spent last weekend weeding out all the pleasure for a Bowdlerised version. "I suppose you could call it a crash course in cultural differences," says Mr Williams.