Ichthyology his pupils continued his ichthyological research. Theophrastus, for example, composed a treatise on amphibious fish. The Romans, although less devoted to science, wrote extensively about fish. Pliny the Elder, a notable Roman naturalist, compiled the ichthyological works of indigenous Greeks, including verifiable and ambiguous peculiarities such as the sawfish and mermaid respectively. Pliny's documentation was the last significant contribution to ichthyology until the European Renaissance. The writings of three sixteenth century scholars, Hippolito Salviani, Pierre Belon, and Guillaume Rondelet, signify the conception of modern ichthyology. The investigations of these individuals were based upon actual research in comparison to ancient recitations.
What Is and What Should Never Be descending riff [of "What Is and What Should Never Be"] is amazing: It's like a bow is being drawn back, and then it releases. The rhythm of the vocals is almost like a rap. It's insane — one of their most psychedelic songs." This was also one of the first songs recorded by the band for which Robert Plant received writing credit. According to rock journalist Stephen Davis, the author of the Led Zeppelin biography "Hammer of the Gods: The Led Zeppelin Saga", the lyrics for this song reflect a romance Plant had with his wife's younger sister. "What Is