CHAPTER XIV. 



NATURAL HISTORY OF THE DIATOMACEiE. 



BY A. MEAD EDWARDS, M. D. 



PREFACE. 



It is desirable that the reader of the present brief ^Icetch should, at the outset, under- 

 stand that it is intended to be of an essentially popular character, and by no means a 

 scientific treatise on the diatomacese. It has been prepared in such a manner that it 

 will, it is hoped, bring to the attention of others besides strictly scientific observers 

 one of the most beautiful groups of organisms with which the naturalist is acquainted. 

 To that end the language employed is as untechnical as was judged consistent with 

 clearness ; and when it has been found necessary to use technical terms, their meaning 

 has been at the same time made plain. This short preface has been intended more 

 specially for the scientist into whose hands this volume may come, so that he may 

 understand its aim and purpose, and, at the same time, not judge it as he would had 

 it made pretence to a position among thoroughly scientific works. At the same time 

 it must be understood that it has of course been made scientifically correct, so that 

 what it teaches concerning the diatomacese may be as nearly as possible up to date, 

 and consistent with the latest investigations in this field of research. 



Introduction. 



TTt is a matter which is well understood at the present day, that if the 

 J% geologist desires to carry out, in a systematic and scientific manner, 

 his investigations into the history of the globe upon which he dwells, 

 he must earnestly and conscientiously qualify himself for extended and 

 searching observations in many more branches of knowledge than his 

 predecessors of but a few years back considered necessary to the accom- 



