PREFACE 



THIS book, as its name implies, is intended to serve as an intro- 

 duction to the subject with which it deals, and not in any way as a 



ERRATA 



Page 188, line 29, "yyrenoids" should be " pyrenoids." 

 Page 202, line 3 from bottom, " hTe " should be "The.' 

 Page 351, lines 8 and 9 from bottom should be transposed. 



it attempts to define the position of these organisms in Nature, and 

 to determine, as far as possible, in this way exactly what should be 

 included under the term " Protozoa," and what should be excluded 

 from the group. Secondly, its function is to guide the student 

 through the maze of technicalities necessarily surrounding the study 

 of objects unfamiliar in daily life, and requiring, consequently, a 

 vocabulary more extensive than that of common language ; and 

 with this aim in view, care has been taken to define or explain fully 

 all technical terms, since confusion of thought can be avoided only 

 by a clear understanding of their exact significance and proper 

 application. Thirdly, it aims at introducing the student to the 

 vast series of forms comprised in the Protozoa and their systematic 

 classification, based on their mutual affinities and inter-relationships, 

 so far as these can be inferred from their structural peculiarities and 

 their life-histories. And, incidentally, attention has been drawn 

 specially to those parts of the subject where the Protozoa throw 



