System of classification Inspired by Johann Phillipp Breyne, Klein developed an interest in science as early as 1713 and began publishing in 1722. He was especially interested in the systematic classification of living organisms, but excluded insects from his classifications. His system was based on external, easily identifiable traits, such as the number, shape and position of limbs. This put his work in opposition with that of Carl von Linné, of whom he was critical, and whose work has since garnered more widespread recognition, though some of Klein's classifications are still in use, for example, in the naming of echidnoderms. His work on sea urchins was the most prominent source of information on the species at the time. His essay Tentamen Herpetologiae (1755) featured the first mention of the term herpetology - the study of amphibians. However, his system of classification meant that species such as frogs and lizards, which belong to amphibians and reptiles respectively, were not distinguished as belonging to separate classes. Klein was critical of Linnaeus' system of classification, believing only easily recognisable features could be used to classify animals, as Adam had done when naming animals according to the Biblical story of creation. Historiae Piscium Naturalis Klein published Historiae Piscium Naturalis promovendae Missus primus Gedani in 1744. The publication, dedicated to the Royal Society, focused on understanding the auditory capacity of cartilaginous and spinose fishes. According to John Eames, until the publication of the work, it was believed to have been understood that only cetaceous fish were known to have auditory passages, or ear holes, and that the question of whether fish could hear was still not understood. Aristotle claimed, in his "History of Animals," that fishes possessed no evident auditory organs, but believed that nonetheless they must hear. In the Preface, Klein cites the work of Giulio Casare Casseri, who discovered bones in the heads of Pike or Jack fish, which he understood to be their organs of hearing, though he did not discover any manifest external auditory passages. In section of the essay titled De Lapillis, eorumque Numero in Craniis Piscium (roughly translated as “The bones, their number in the skull of Fish”) Klein considers what parts of the head of fish serve as the organ of hearing, and by what passages the sensation of sound is communicated to them. He refers to these bones as Ossicula – little bones – and considers them