80 Arctic Natural History. 



of ice in the Arctic Regions sometimes consists of the remains 

 of algae, either in a state of decomposition or reduced to a 

 pulp by the abrading action of drifting bergs, &c. ; such at 

 least was the nature of specimens examined by me several 

 years ago. 



In conclusion, it may be observed how few species there 

 are of the olive- coloured and red algae ; such as are recorded 

 may be considered as fairly representing these plants in the 

 parts visited by the Expedition. The number of littoral species 

 in such regions must be few, or in many places altogether 

 absent ; the continual abrading influence of bergs and pack 

 ice would effectually prevent their growth. 



In the thinning out of algae in such latitudes, it is a point 

 of interest to ascertain what genera and species resist longest 

 the influence of conditions inimical to the development of 

 vegetable organisms. Only five of the olive- coloured series 

 are recorded here, four of which are British ; the fifth, viz., 

 the Agarum, being exclusively an American form. Of the 

 red series there are only three ; one of them, the Polysiphonia, 

 being a common species in Britain, the Dumontia is an 

 American form, the third, new. 



The green Algse are better represented, six being marine, 

 and fourteen from fresh water or moist places on land, con- 

 firming the opinions entertained respecting the more general 

 diffusion of the green than of the olive and red. Of the 

 twenty enumerated, about a third are British. 



Of Desmidieae, only three were detected in Dr Sutherland's 

 collection, two of which are British, and the Arthrodesmus 

 has been found in France and Germany. 



The Diatomaceae, as might have been expected, are numer- 

 ous. Their importance in reference to the existence of ani- 

 mal life in high latitudes has been already alluded to ; an 

 importance out of proportion to their size, the generality of 

 them being so minute that their presence can only be detected 

 by the microscope ; or rather, it may be remarked, that their 

 minuteness renders them important, since they are readily 

 conveyed to the digestive organs of mollusca by currents pro- 

 duced by the numerous cilia on the mantle and gills of these 

 animals. By a wise arrangement their numbers compensate 



