2 INTRODUCTION 



of animals, but such attempts were not generally understood or followed, 

 and most authors still employed unnatural methods of arranging them. 

 Many still followed Pliny and grouped animals according to their environ- 

 mental conditions, placing those together having similar methods of life, 

 as land animals, fresh-water animals, marine animals, flying animals, 

 etc. Within each group the species were often arranged in alphabetical 

 order. 



LinnaBus' system was very quickly accepted by the scientific world 

 and went into universal use, and modern zoology may, in a very real sense, 

 be said to begin with the year 1758. 



So radical, however, was Linnaeus' reform that neither the superiority 

 of his system nor the simplicity of his terminology would probably have 

 been sufficient thus to procure its instant adoption if they had not been 

 proposed by a man of his great fame and commanding position in the 

 world. Linnaeus was considered by his contemporaries, because of his 

 numerous and important contributions to science and his eminence as a 

 teacher in the University of Upsala, as the greatest naturalist of all time. 

 His importance was indicated by the phrase in vogue: Deus creavit; 

 Linn&us disposuit. 



The immediate acceptance of the Linnaean classification had the same 

 effect upon the study of animals and plants in his day as that of Darwin's 

 theory of natural selection had almost exactly one hundred years later. 

 It gave a tremendous impetus to every branch of biological investigation 

 and started a new era. Systematic zoology, morphology, physiology, and 

 experimental zoology all attracted able investigators, who studied them 

 with feverish activity. Comparative studies first became possible as now 

 the facts of the science were for the first time arranged in something like 

 an orderly and natural manner, and the next generation saw the rise of the 

 sciences of comparative anatomy, paleontology, and comparative embry- 

 ology, and also the first modern speculations on the blood relationships and 

 the evolution of living things. 



All these things gave a new importance to zoology and raised it from 

 the position it had occupied of a mere annex to medicine to the dignity of 

 an independent science. 



Linnaeus divided the animal kingdom into six classes: Mammalia, 

 Aves, Amphibia, Pisces, Insecta, and Vermes. The knowledge of this last 

 class, which included all invertebrate animals except the arthropods, was 

 in a very confused state and one of the chief objects of the many able 

 zoologists of the generation immediately following him was to remedy this 

 condition. The men whose services were greatest in this direction were 

 0. F. Miiller, Lamarck, and Cuvier. In 1794 Lamarck first distinguished 

 the vertebrates from the invertebrates and divided the Linnaean class 



