PREFACE TO THE SIXTH EDITION. 



A PEW additions and alterations, based upon a continuous 

 working knowledge of the book since its first issue, have been 

 made in this edition. Professor Marshall had so complete a 

 grasp of the difficulties which confront a student of Elementary 

 Zoology, and so great a sense of proportion and arrangement, 

 that no substantial alteration could increase the educational 

 value of his work. 



Two new figures have been added, Figs. 30 and 37. For the 

 second of these, taken from Professor Marshall's " Vertebrate 

 Embryology," I am indebted to Messrs. Smith, Elder & Co. 



G. H. F. 



Univebsity College, 

 London, 1896. 



