INTRODUCTION. 



Algae, which he had preserved for examination in a separated 

 and confined condition. 



The above comprises all the information on the present sub- 

 ject hitherto accessible to the English reader, if we except a few 

 remarks on the physiology of the process in Professor Braun's 

 ' Rejuvenescence in Nature ' (published by the Ray Society, 

 1853), and which refer rather to the facts recorded by Mr. 

 Thwaites, than to personal observations of the ingenious writer. 



I now proceed to record the various examples of the conju- 

 gating process which have fallen under my own observation, and 

 to deduce from the whole such conclusions respecting its nature 

 and significance as may appear legitimate and necessary. I 

 shall mention, in the order of their systematic arrangement, the 

 species in which I have noticed conjugation, with the date of 

 the observation, and shall add a reference to the figures in the 

 Plates of the present volume which illustrate the process under 

 its various modifications : — 



1. Epithemia turgida, W. Sm., September 1847. Plate A. fig. 2. 1.-IV. 



(from Thwaites). 



2. Epithemia Zebra, October 1848. 



3 ] M Sorex, Kutz., May 1851. Plate A. fig. 9. I. II. 



4_ sj gibba, Kutz., September 1847. Plate A. fig. 13. I. II. 



5 }> ventricosa, Kiitz., November 1853. Plate A. fig. 14. 1. II. 



6. Cocconeis Placentula, Ehr., February 1853. Plate B. fig. 32. 1.-IV. 



7. Cyclotella KutzingiaNa, Thw., November 1848. Plate B. fig. 47. 



I.-IV. 



8. Cocconema lanceolatum, Ehr., January 1850 and April 1852. 



Plate C. fig. 219. 



9. Cocconema Cistula, Ehr., August 1850 and April 1852. Plate C. 



fig. 221. I. II. 



10. Cocconema parvum, W. Sm., April 1850. 



11. Gomphonema dichotomum, Kutz., August 1850. Plate C. fig. 240. 



12 . „ tenellum, W. Sm., March 1853. 



13 }> olivaceum, Ehr., March 1850, April 1852 and March 

 1853.' Plate D. fig. 244. I.-IV. 



14 Gomphonema curvatum, Kiitz., March 1849. Plate C. fig. 245. I.-IV. 

 15 [ n M ARiNUM,W.Sm., March 1852. Plate D. fig. 246. 1.-V. 



16. Himantidiumpectinale, Kiitz., October 1847. PlateD. fig. 280. I.-IV. 



(from Thwaites). 



17. Achnanthes longipes, Ag., July 1849. 



18# m „ /3, W.Sm., March 1852. Plate D. fig. 300/3. 



i. -in. 



