PEEFACE TO YOL. II. 



The proof sheets of this volume, like those of the last 

 volume, have been looked through by Dr. Hooker and Prof. 

 Huxley; and I have, as before, to thank them for their 

 valuable criticisms, and for the trouble they have taken in 

 checking the numerous statements of fact on which the argu- 

 ments proceed. The consciousness that their many duties 

 render time extremely precious to them, makes me feel how 

 heavy is my obligation. 



Part IV., with which this volume commences, contains 

 numerous figures. Nearly one half of them are repetitions, 

 mostly altered in scale and simplified in execution, of figures, 

 or parts of figures, contained ia the works of various 

 Botanists and Zoologists. Among the authors whom I have 

 laid under contribution, I may name Berkeley, Carpenter, 

 Cuvier, Green, Harvey, Hooker, Huxley, Milne- Edwards, 

 Balfs, Smith. The remaining figures, numbering 150, are 

 from original sketches and diagrams. 



The successive instalments which compose this volume, 

 were issued to the Subscribers at the following dates : — No. 

 13 (pp. 1—80) in January, 1865; No. 14 (pp. 81—160) in 

 June, 1865 ; No. 15 (pp. 161—240) in December, 1865 ; No. 

 16 (pp. 241—320) in June, 1866 ; No. 17 (pp. 321—400) in 

 November, 1866 ; and No. 18 (pp. 401— 566) in March, 1867. 



London, March 2ord, 1867. 



