Red kangaroo has the ability to freeze the development of an embryo until the previous joey is able to leave the pouch. This is known as diapause, and will occur in times of drought and in areas with poor food sources. The composition of the milk produced by the mother varies according to the needs of the joey. In addition, red kangaroo mothers may "have up to three generations of offspring simultaneously; a young-at-foot suckling from an elongated teat, a young in the pouch attached to a second teat and a blastula in arrested development in the uterus". The kangaroo has also
What Is This Thing Called Love? (short story) with aliens and sex. According to Asimov the article was mostly based on "Marvel" since its contents had been the raciest. Cele Goldsmith Lalli, editor of "Amazing Stories", requested a satire of the "Playboy" article. Asimov set out to write a story telling how a sex-interested alien and humans might "really" interact. The story appeared in the March 1961 issue of "Amazing" as "Playboy and the Slime God", but when Asimov included it in his 1969 collection "Nightfall and Other Stories" he retitled it "What Is This Thing Called Love?" Goldsmith Lalli rewrote the story's last three paragraphs, a change