568 Microscopic Life in the Ocean at the South Pole. 



there ; and likewise on a ship, which, according to the account in 

 his letter, was 380 sea-miles distant from land. The wind was then 

 blowing from the African coast. Mr. Darwin has sent to the author 

 for examination a sample of the dust which fell on the ship on the 

 high sea at that great distance from land. This dust has been uni- 

 versally regarded hitherto as volcanic ashes. The microscopic analy- 

 sis has clearly shown that a considerable portion, perhaps one-sixth 

 of the mass, consists of numerous speceis of Siliceous Polygastrica 

 and portions of silicated terrestrial plants, as follows : — 



A. SILICEOUS POLYGASTRICA. 



1 Campylodiscus Clypeus. 



2. Eunotia Amphioxys. 



3. ... gibberula. 



4. Gallionella crenata. 



5. ... distans. 



6. ... granulata. 



7. ... marchica. 



8. ... procera. 



9. Gomphonema rotundatum ? 



10. Himantidium Arcus. 



11. ... Papilio. 



12. Navicula affinis ? 



13. ... lineolata. 



14. ... Semen. 



15. Pinnularia borealis. ? 



16. ... gibba. 



17. Surirella (peruviana?) 



18. Synedra Ulna. 



B. SILICEOUS PHYTOLITHARIA. 



19. Amphidiscus Clavus. 



20. Lithodontium Bursa. 



21. ... curvatum. 



22. ... furcatum. 



23. ... nasutum. 



24. ... truncatum. 



25. Lithostylidium Amphiodon. 



26. ... clavatum. 



27. ... cornutum. 



28. ... lseve. 



29. Lithostylidium Ossiculum. 



30. ... quadratum. 



31. ... rude. 



32. ... Serra. 



33. ... spiriferum. 



34. Spongolithis acicularis. 



35. ... aspera. 



36. ... mesogongyh 



37. ... obtusa. 



The forms included in this catalogue, mostly known and for the 

 most part European, prove — 



1. That this meteoric shower of dust was of terrestrial origin. 



2. That it is not volcanic ash. 



3. That it was dust which had been lifted up to a great height 

 from a dried-up marshy district by an unusually strong current of air 

 or a whirlwind. 



