PREFACE. 



THE main object in the preparation of this work 

 was to bring together, as concisely and accurately 

 as possible, in a single manual, .all that has been 

 so far discovered regarding the British Freshwater 

 Rhizopoda and their near allies the Heliozoa. The 

 labours of Dr. Penard of Geneva have resulted in 

 his giving to the world exceedingly valuable mono- 

 graphs of the Rhizopoda and Heliozoa of Central 

 Europe, and of Switzerland in particular; and it 

 is to be regretted that no British Biologist of 

 equal standing has done the same for this country, 

 which is certainly not less rich in species. 



The present attempt at a classified description 

 of these microscopic animals will it is hoped lead 

 to other workers entering upon a field of research 

 which is fascinating in a high degree even to the 

 general microscopist. The biological student will 

 find in this manual an honest effort, at least, to 

 describe the species which have hitherto been met 

 with in this country, to give their usual habitats, 

 and to point out the characters by which they may 

 be most easily identified. 



I do not profess to have investigated very close- 

 ly the physiological problems associated with the 

 life-histories of these organisms ; the minute and 

 continuous observations which are necessary for that 



