Vi PREFACE 



and C. T. Holford, and Messrs. L. Archbutt, G. H. 

 Broom, and R. Lyon. Their thanks are also due to 

 manufacturers and their representatives for the loan of 

 valuable apparatus and of blocks for many of the figures 

 in the text. 



Several of the illustrations are from photomicrographs 

 of objects procured from slide-lending libraries. Access 

 to slides which have been mounted by specialists is in- 

 valuable for practice in photomicrography and for the 

 study of objects otherwise unobtainable, but the worker 

 is strongly recommended to make his own preparations 

 whenever possible. As a help in that direction the 

 methods adopted in preparing some of the objects illus- 

 trated in the plates are described. 



In conclusion we must recognise with thanks the great 

 care and courtesy with which the Publishers have always 

 met our wishes in regard to the illustrations and general 

 arrangement of the book. 



H. L. H. 

 W. B. R. 



November, 1913. 



