X THE HISTORY OP THIS WORK. 



Heliozoa, but as his reason was that he had so little 

 material, I thought that by the time the third volume 

 would be required many more species might be found, 

 and urged him to continue to collect and record them. 

 It was then also, seeing his method of collecting from 

 sphagnous pools, that I commenced to collect. 



It may be well to state here that nearly all the 

 Freshwater Rhizopoda are so minute that they cannot 

 be detected with a hand-lens, requiring a compound 

 microscope for their detection as well as examination. 

 The records to which no name is attached are those of 

 Mr. Cash ; nearly all others except published records 

 are the result of the examination of material sent to 

 him — that material being chiefly species of Sphagnum 

 or of some other bog-moss. It was his intention to 

 state this in his Preface to this volume. 



Mr. Cash was a botanist as well as a zoologist, but 

 as a sketch of his life is promised by Mrs. Cash for a 

 future volume, it will be best to defer to that any 

 appreciation of his scientific work. I wish however to 

 express here my thanks to Mrs. Cash for her kindness 

 in placing in my hands all her husband's manuscripts 

 relating to the Rhizopoda (but mostly unintelligible, 

 being in a shorthand of his own device), and also all 

 his drawings of them; and for presenting to me 

 recently a valuable collection of microscopic prepara- 

 tions of freshwater rhizopods made by Dr. Penard of 

 Geneva and given to Mr. Cash by him. 



I have also to thank Dr. Penard for adding to that 

 collection, and for his kind assistance in reading the 

 first proofs of this volume and making critical remarks 

 which I have greatly appreciated and have made 

 use of so far as was practicable in a text with the first 

 proof set up in pages. 



