A MANUAL 



OF THE 



COMMON INVERTEBRATE ANIMALS 



EXCLUSIVE OF INSECTS 

 INTRODUCTION 



1. The Linncean system of classifying animals. The foundation of 

 the modern system of classifying animals was laid by Carolus Linnaeus 

 in the tenth edition of his Systema Naturae, published in 1758. In this 

 epoch-making work he first applied his fully developed binomial method 

 of classification to the animal kingdom and arranged all the animals 

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

 and species. 



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

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

 one, or 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 features 

 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 the new 

 ones which were constantly being discovered. But the names given were 

 often complex and cumbersome and no uniformity existed between the 

 systems of terminology of different authors. Also the custom of giving 

 two or more Latin names to a species was frequently in vogue, but a 

 binomial system, with the definite relation of the specific to the generic 

 name, was new. The genus, which gives the clue to the natural affinities of 

 the animal, was peculiarly Linnaeus' invention. 



Attempts had also been made by Ray and Klein and other advanced 

 thinkers to form a system which should express the natural relationships 



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