

PREFACE TO THE SECOND 

 EDITION 



IT has been the author's intention, should 

 a second edition of this book be demanded, 

 to revise the chapters dealing with the 

 development of the frog and chick, and to add 

 a brief chapter upon the development of the 

 mammal. The second part of this purpose has 

 been carried out in the new chapter Chapter 

 IX of the present edition, but this edition 

 having been unexpectedly called for, the au- 

 thor has been unable, owing to pressure of 

 other work, to do more than make the addition 

 referred to, and correct a few typographical 

 errors in the original chapters. 



In what is said of the development of the 

 mammal the chief aim has been to call attention 

 to the main points of difference between the 

 development of the bird and that of the mam- 

 mal, and to explain the more difficult features 

 in mammalian development. 



