X PREFACE 



eluded first; the others are added for those instructors who can 

 give more time to natural history. At the end of each chapter 

 is included a brief discussion of the embryology of the class, 

 placed in a distinct section, so that it may be conveniently 

 omitted. This omission will probably be desirable in curricula 

 where a course in embryology follows comparative anatomy. 



Comparative Morphology, part ii, is a study of the compara- 

 tive development and form of the organic systems. Reference is 

 made to fossil evidence in places where it does not entail a knowl- 

 edge of stratigraphy. Emphasis is placed upon the dogfish and 

 the mammal, as most half-year courses are limited to a laboratory 

 study of these two forms. It is assumed that most of Part II 

 will be covered in the course. The chapter on ''Mechanics of 

 Development" is included, as this phase of anatomy has gained 

 unusual prominence in anatomical research during the past few 

 years. 



Evolution of the Vertebrates, part hi, takes up the palaeon- 

 tological evidence and some other points of interest which are 

 necessarily omitted in the first two parts, and includes a chapter 

 on Geographical Distribution. This material may be assigned 

 as collateral reading, or omitted. The chapter entitled ''Adaptive 

 Radiations of the Vertebrates" is designed as a summary of the 

 courses which vertebrate evolution has followed. It is felt that 

 a review of the lines of evolution tends to coordinate the evi- 

 dence which has been gained in a study of individual systems. 



It is my hope that the book in part meets the objections of my 

 students, both pre-medical and general, to the books previously 

 assigned to them; and that it complies with the following re- 

 quests : (1 ) that unnecessary detail be omitted, particularly those 

 details which apply to small groups and have little comparative 

 significance; (2) that ordinal relationships rather than specific 

 comparisons be given, so that laboratory work can be correlated 

 more easily; (3) that generic names be omitted wherever possible 

 and explained when used, as few students are taxonomists; and 

 (4) that less be left to the imagination when comparing gen- 

 eralized mammalian and human structures. 



