While the physicians of the Rhineland were describing and figuring their native plants, the study of animals began to revive. Two very different methods of work were tried by the zoologists of the sixteenth century. One set of men, who may be called the Encyclopædic Naturalists, were convinced that books, and especially the books of the ancients, constituted the chief source of information concerning animals and most other things. They extracted whatever they could from Aristotle, Ælian, and Pliny, adding all that was to be learned from the narratives of recent travellers, or from the collectors of skins and shells. The books on which they chiefly depended, being for the most part written by men who had not grappled with practical natural history and its problems, were unfortunately altogether inadequate. Many of the statements brought together by the encyclopædic naturalists were ill-attested; some were even ridiculously improbable. If inferences from the facts were attempted—and this was rare—they were more often propositions of morality or natural theology than the pregnant thoughts which suggest new inquiries. Hence the encyclopædic plan, even when pursued by men of knowledge and capacity, such as Gesner and Aldrovandi, yielded no results proportional to the labour bestowed upon it; the true path of biological progress had been missed. Naturalists of another school described and figured the animals of their own country, or at least animals which they had closely studied. Rondelet described from personal observation the fishes of the Mediterranean; Belon described the fishes and birds that he had met with in France and the Levant. His _Book of Birds_ (1555) is a folio volume in which some two hundred species are described and figured. The "naturel" (natural history of the species) contains many curious observations. Perhaps the best things in the book are two figures placed opposite one another and lettered in correspondence; one shows the skeleton of a bird, the other that of a man. The example of Rondelet and Belon was followed by other zoological monographers, who did more for zoology than all the learning of the encyclopædists. Early Notions of System.