viii PREFACE 



familiar biological terms. I have endeavoured to 

 avoid this pit-fall, but have doubts as to the com- 

 pleteness of my success. I shall be obliged therefore 

 if readers will point out passages which require 

 elucidation, so that, in the event of another edition 

 being published, the defects may be remedied. 



FREDERICK KEEBLE. 



TRE"GASTEL, 



COTES-DTJ-NORD, 



FRANCE. 

 September, 1910. 



