PREFACE TO THE SECOND EDITION. 



When this little work first appeared, it was put for- 

 ward as a Part I, to be followed by other Parts. That 

 plan was however soon abandoned. Nevertheless the 

 volume seemed to have a place of its own ; and my dear 

 lost friend undertook to prepare a second edition, in- 

 tending to add some account of the development of 

 the Mammal with a view of making the work an 

 elementary introduction to vertebrate embryology more 

 particularly suited for medical students. He was occu- 

 pied with the task at the time of his sad death; and 

 indeed a melancholy interest is attached to some of the 

 sheets, by the fact that he had taken them to Switzer- 

 land with him, on that fatal journey. 



All the first part up to p. 160 he had passed for 

 press ; and he had further revised up to about p. 202. 

 The whole of the rest of the volume has been under- 



