INTRODUCTION 5 



animals possessing the essential characteristics of the vertebrate type. 

 The formation of this phylum has been due to the fundamental researches 

 of Kowalevsky, who in 1866, 1867, and 1871 gave the first detailed and 

 accurate descriptions of the anatomy of Balanoglossus and also the first 

 detailed account of the embryology of ascidians and of Amphioxus, show- 

 ing that these animals are related to one another and to vertebrates. The 

 term Chordonia was introduced in 1874 by Haeckel to include the Tuni- 

 cata, Amphioxus, and the Vertebrata, and the terms Urochorda and 

 Cephalochorda by Lankester in 1878 for the Tunicata and Amphioxus. 

 In 1884 Bateson, on the basis of his researches on the American form 

 Balanoglossus aurantiacus, added the Enteropneusta to the Chordata and 

 proposed the term Hemichorda. 



The system of zoological classification was thus fixed some twenty or 

 thirty years ago and has undergone no important changes in its larger 

 features since. This is not true, however, of many of the subordinate and 

 smaller of its groups, the arrangement of which changes from time to 

 time as the knowledge of the relationships of the animals composing them 

 increases. We find this to be especially true of certain low animals 

 which seem to be isolated side branches of the ancestral tree, the origin 

 of which from the main stem is still obscure. 



2. The study of animals in America.* The earliest notices of Amer- 

 ican animals are to be found in the numerous descriptions of the country 

 and books of travel in America which were published in Europe during 

 the sixteenth, seventeenth, and eighteenth centuries. In Linnaeus' twelfth 

 edition over 500 species of North American animals were described, of 

 which 78 were mammals and 260 were birds. Of the authors quoted 

 in these descriptions perhaps the most important were Mark Catesby and 

 Peter Kalm. The former was an Englishman who lived in the southern 

 English colonies of America for about ten years between 1712 and 1726 

 and published a large illustrated work on the natural history of the 

 region. The latter was one of Linnaeus' pupils who spent the years 

 between 1747 and 1751 in Canada and the central English colonies col- 

 lecting and studying the native animals and plants for him. Linnaeus 

 also obtained much information by correspondence with American nat- 

 uralists, especially Dr. Alexander Garden of Charleston, Dr. John Mitchell 

 of Virginia, and John Bartram of Philadelphia. Thus in 1766 probably 

 most of the larger and more conspicuous animals of the eastern part of 

 the country were known to science, as well as many insects and other 

 smaller ones. 



* See "A Century's Progress in American Zoology," by A. S. Packard, Jr., Am. 

 Nat. Vol. 10, p. 591, 1876. "The Beginnings of American Science," by G. B. Goode, 

 Ann. Rep. Smiths. Inst. for 1897, Pt. 2, p. 409. 



