How the Snake Lost Its Legs fly embryo. His books on evolutionary developmental biology (evo-devo) include "Imaginal Discs: The Genetic and Cellular Logic of Pattern Formation" (2002), "Quirks of Human Anatomy: An Evo-Devo Look at the Human Body" (2009), and "Deep Homology? Uncanny Similarities of Humans and Flies Uncovered by Evo-Devo" (2017). In Held's view, "Quirks", "Snake", and "Deep Homology" form a trilogy on evo-devo. "How the Snake Lost Its Legs" is ostensibly organised into six chapters, but in effect into three parts. The first chapter serves as an introduction and overview. The next four chapters provide what Held calls "the meatier aspects of evo-devo" with
How Many More Times Wolf's "How Many More Years" (1951), as well as other songs by blues musicians he admired at the time of recording. In 1970, "How Many More Times" was dropped from Led Zeppelin's typical setlist, although they continued to perform it on occasion until the early stages of their 1975 North American tour, when it was re-introduced in full as a result of Jimmy Page's injured finger, which temporarily prevented him from playing the more challenging "Dazed and Confused". In a contemporary review for "Led Zeppelin" on release, John Mendelsohn of "Rolling Stone" called "How Many More Times" as the album's