PREFACE. 



wholly at first : that by Dr. Ehrenberg has met with its 

 share of opponents. The principal arguments respecting 

 it will be found herein ; so that the student, having both 

 sides of the question before him, will be able to arrive at a 

 fair conclusion. 



The translation of Die Infusionsthierchen was made for 

 me by Dr. Willshire ; that excellent botanist has also 

 compared my manuscript of Part II. with that work, 

 so that the materials taken therefrom are, no doubt, 

 correctly given. Since Dr. E.'s volume appeared, some 

 discoveries in Fossil Infusoria have been made ; these, 

 and the Spermatozoa of plants, unknown in this coun- 

 try, I have introduced. Information derived from other 

 sources is duly acknowledged. 



A few words seem necessary regarding the drawings. 

 Those for plate xii. were kindly furnished me by that 

 venerable and distinguished botanist, Dr. Unger, of Gratz, 

 and the late eminent microscopic observer, Mr. F. Bauer. 

 Every original drawing has the artist's name mentioned in 

 the description of it, and the -others, with few alterations, 

 are from Die Infusionsthierchen. The labour and time 

 occupied in selecting, reducing, arranging, and condensing 

 these, was far greater than most persons would imagine, 

 and has been augmented by the discovery, after some 



