INTRODUCTION. 



Section VIII. 



Reproduction in the Diatomace^e. 



I have already said (Introduction, vol. i. p. xxviii) that " the 

 circumstances which accompany the reproduction of the Dia- 

 tomacese are too imperfectly understood to permit me to 

 employ them, as I ought otherwise to have done, in the generic 

 arrangement of the species." The three years which have 

 elapsed since I penned this sentence have not materially added 

 to the knowledge then possessed on this interesting portion of 

 our inquiry. The phenomena which attend the formation of 

 the reproductive body are still altogether unknown in many 

 genera, and are only partially understood even where they have 

 been best observed and most carefully recorded. 



The little hitherto known upon the subject is primarily due 

 to the researches of Mr. Thwaites, abruptly terminated by his 

 removal to another and wider field of labour, amidst the more 

 luxuriant and attractive vegetation of a tropical climate. 



In July 1847, Mr. Thwaites announced, in the pages of the 

 ' Annals of Natural History,' that he had discovered, in the 

 May of that year, a species of the Diatomaceae, viz. Eunotia 

 turgida, Ehr. (Epithemia turgida, Kiitz., and Synop. B. D. vol. i. 

 fig. 2), in a state of " conjugation." 



He was led to adopt this term from the analogy which the 

 process he had detected bore to that occurring in the Bes- 



