INTRODUCTION 9 



Under the leadership of Alexander Agassiz and E. L. Mark, but 'also in 

 Baltimore where Louis Agassiz's pupil W. K. Brooks taught in the newly 

 founded Johns Hopkins University. From these two centers the scientific 

 study of animals has spread to almost all the universities and other institu- 

 tions of learning of the country, and the men who have gone out from them 

 all year by year in ever increasing numbers have maintained the high stand- 

 ards which Agassiz represented and have today placed American scholar- 

 ship in this field in the fore rank of the world's achievement. 



Very important in the history of American zoology was the estab- 

 lishment, a few years after the death of Louis Agassiz, of the Woods 

 Hole Marine Biological Laboratory (1887), The Journal of Morphology 

 (1888), and the Morphological Society (1890). These enterprises were 

 due very largely to the initiative of C. 0. Whitman and brought about a 

 solidarity of interest of the scientific zoologists of the country to which 

 the great advances made by zoological investigation in America in recent 

 years and the high rank it has attained in the world are largely due. 



Important also has been the part taken by the various scientific de- 

 partments of the United States government in furthering the study of 

 animals. This work was begun by the Smithsonian Institution in 1846 

 and has been continued directly by it and the United States National 

 Museum, the Bureau of Fisheries, the Geological and Coast Surveys, the 

 Marine Hospital, and the various Bureaus in the Department of Agri- 

 culture. The important scientific work carried on by these institutions 

 and the great collections they have accumulated have made Washington 

 today the most important scientific center in the country. 



3. Subdivisions of the animal kingdom. The animal kingdom con- 

 tains in this book eight subkingdoms or phyla. Several of these are sub- 

 divided into subphyla, and all the phyla and subphyla into classes. The 

 classes are made up of orders, although they are sometimes first sub- 

 divided into subclasses and these into orders. The orders, and the sub- 

 orders into which some of them are subdivided, are made up of families, 

 and often subfamilies. Each family and subfamily is composed of one 

 or more genera and each genus of one or more species. The combination 

 of its generic with its specific name constitutes the scientific name of an 

 animal. 



The whole number of species of animals* which make up the animal 

 kingdom is not known but probably amounts to several million. The 

 number which has been described in scientific publications and given 

 names in the Linna3an system of classification is considerably over half 

 a million. 



* See "On the Number of Known Species of Animals," by H. S. Pratt, Science, 

 N. S., Vol. 35, p. 467, 3912. 



