viii Preface 



tion. Biology is something more than an "interesting science" whose* 

 devotees collect pretty butterflies, prepare nice white skeletons, and 

 record songs of birds. Our present total knowledge of the chordates has 

 a life-or-death significance for the human chordate at this present 

 moment in the history of his race. 



The plan of the book is calculated to reduce the difficulties about 

 placing the treatments of embryology and classification in logical rela- 

 tion to descriptive comparative anatomy. Part I describes the basic 

 structure of vertebrates — i.e.. the structural features which are com- 

 mon to all vertebrates. There is little comparative anatomy in this part. 

 The several chapters on basic structure supply ample background for 

 the immediately following chapters on embryology and histology. 

 Part II comprises the historical and theoretic chapters. The chapter on 

 "Aim; and Method of Comparative Anatomy" is placed here so that 

 the reader may have clearly in mind the significance of homology and 

 the meaning of such terms as "convergence," "parallelism," etc., before 

 passing on to the comparative description in Part III. This part 

 includes not merely vertebrates but all chordates, and its comparative 

 anatomy is supplemented, so far as need be, by comparative embryol- 

 ogy; hence the title "Comparative Morphology of Chordates." The 

 arrangement is by Classes. In the treatment of each Class the basic 

 structure is assumed and the description confines itself to those 

 specialized features which, superimposed upon the basic structure, 

 make the animal a fish, amphibian, reptile, bird, or mammal. The 

 animals of each Class are compared to those of the preceding (in 

 phylogenetic sense) Classes. Hence the comparative treatment expands 

 from a minimum in the chapter on fishes and amphibians to a maximum 

 in the chapters on mammals. The detailed classification succeeds the 

 descriptive and comparative account of the group. 



The chapters on "Reproduction" and "Histology" and the section 

 on endocrinal organs (in Chapter 6) have been taken, with considerable 

 revision, from the corresponding parts of "Comparative Anatomy" by 

 Neal and Rand. Numerous illustrations have been taken from the 

 books ("Comparative Anatomy" and "Chordate Anatomy") by Neal 

 and Rand. Many of them, conceived and executed by Professor Neal, 

 pay eloquent tribute to his rare combination of competence as an 

 anatomist and skill as an artist. 



Mention of all persons to whom the author feels under obligation for 

 assistance and encouragement in the preparation of the book would 

 unduly extend the length of this preface. His acknowledgments must be 

 restricted to the following few whose help has been of a quite specific 

 or tangible sort: to Alfred S. Romer, Director of the Museum of Com- 

 parative Zoology at Harvard University, who, in response to a request 



