VI 



PREFACE TO THE FIFTH EDITION. 



The principal changes in the present edition are in the chapter 

 on Embryology, in which some new figures have been intro- 

 duced and some mistakes corrected. 



In revising the book I have received valuable aid from my 

 friends Dr. Hurst and Mr. Gamble, Assistant Lecturers in 

 Zoology in the College. 



Owens College, 



December^ 1893. 



NOTE. 



The preparation of the present (fifth) edition for the printer 

 was Professor Marshall's last professional act, and was com- 

 pleted only a week before his death. 



In correcting the proofs I have made no change of any 



importance. 



C. Herbert Hurst. 



Owens College, 



April, 1894. 



