298 THE POPULAR SCIENCE MONTHLY 



THE FOUR PEEIODS IK THE DEVELOPMENT OF THE 

 MODEEN ZOOLOGICAL SYSTEM 



By Professoe H. S. PRATT 



HAVEEFOED COLLEGE 



IN" 1758 when Linnseus published the epoch-making tenth edition of 

 his " Systema Naturge " the science of zoology was in a backward 

 condition, having made but little progress for a long period of time. 

 Some important advances, it is true, had been made by the generation 

 immediately preceding that event. Trembley and Peysonnel had proved 

 the animal nature of Hydra and of corals; Linck and Klein had in- 

 creased the knowledge of the obscure group of echinoderms; Eeaumiir 

 had continued the brilliant researches of Swammerdam on insects. The 

 discovery of microscopic animals, also, in the preceding century, had 

 opened up new vistas, into which, however, the scientists of the day saw 

 as yet but dimly. Zoology was still, notwithstanding these things, a 

 very crude descriptive science, in which but few fruitful attempts at 

 comparative or philosophical studies had been made. 



The cause of this failure to progress rapidly was not the lack of 

 able and earnest zoologists in the preceding ages or even the absence of 

 new discoveries, but the chaotic condition of the zoological classification 

 and nomenclature, which stood in the way of the recognition of the 

 true relationships of animals. A chaos could not become the basis of a 

 system of philosophy. When thus in 1758 Linnaeus introduced his 

 fully developed binomial system and arranged all the animals then 

 known to science according to its rules into classes, orders, genera and 

 species he provided the key which should unlock the mysteries of zool- 

 ogy as a science, and disclosed the wonders it contained. 



The essential feature of this system and that which was new at the 

 time was the giving to each species of animals of two names, instead of 

 one, or of several, one of which was the specific name and the other the 

 name of the next higher subdivision in the classification, the genus. 

 The other important features were the precisions of the terminology 

 employed, which enables the author to characterize a species in a few 

 words, and the natural arrangement of the classification in which the 

 position of each species indicates the degree of its genetic relationship 

 to all the others. 



It is true that predecessors of Linnaeus had anticipated many fea- 

 tures of his system. The idea of a species was already well fixed before 

 his time and efforts were made to characterize those then known and 



