viii PKEFACE 



I should like especially to mention Professor Poulton, Professor 

 Herbert Jackson, Dr. Stapf, Dr. Daydon Jackson, Dr. Sibly and 

 Professor G. E. Nicholls ; while to Mr. E. W. H. Eow, of the 

 Zoological Department at King's College, I am much indebted 

 for the trouble which he has taken in reading through the 

 proof-sheets and for many valuable suggestions. 



I owe a sincere acknowledgment to my publishers, Messrs. 

 Constable & Co., for their generosity in the matter of illustrations. 

 Most of these are either entirely new or, in some cases, specially 

 re-drawn from original memoirs. I have made extensive use of 

 photomicrography for microscopic subjects, and in the prepara- 

 tion of the photographs at King's College have received much 

 assistance from Dr. Eosenheim, Mr. Eow, and my assistant 

 Mr. Charles Biddolph. 



For the loan of the blocks from which the remainder of the 

 illustrations have been printed, or for permission to copy, I am 

 indebted to the generosity of the following : 



Messrs. George Allen and Son, 



" The American Journal of Science," 



Mr. Edward Arnold, 



Messrs. George Bell and Sons, 



Messrs. A. and C. Black, 



The Cambridge University Press, 



The Clarendon Press, 



Messrs. Constable & Co., 



Messrs. Duckworth & Co., 



Herr W. Engelmann, 



Herr Gustav Fischer, 



" The Journal of Experimental Zoology,'' 



Messrs. Kegan Paul, Trench, Triibner & Co., 



The Council of the Linnean Society of London, 



Messrs. Longmans, Green & Co., 



Mr. John Murray, 



" The Quarterly Journal of Microscopical Science," 



The Council of the Eay Society, 



Messrs. Smith, Elder & Co., 



The Trustees of the British Museum, 



Messrs. T. Fisher Unwin, 



Messrs. F. Warne & Co., 



Verlag des Bibliographischen Instituts, Leipzig und Wien. 



