150 THE OCEAN 



toriaceae, and something similar occurs in the 

 ocean. The best-known oceanic genus is Tricho- 

 desmium, consisting of brownish, yellow, or 

 red cells collected together into little bundles, 

 which have in the water the appearance of 

 chopped hay. In calm weather these clusters 

 rise to the surface by means of air vacuoles, 

 and at times form a yellowish-brown scum of 

 great extent, which is called by sailors 

 " whales' spawn." When this scum occurs 

 in great quantity a disagreeable pungent smell 

 is given off, and sometimes it has an ill effect 

 on the eyes and nose. Other species of Oscil- 

 latoriaceae are known to have noxious proper- 

 ties. These blue-green algae, in addition to 

 chlorophyll, contain phycocyanin and other 

 colouring matters, which modify the absorp- 

 tion spectra, and thus affect the assimilation 

 of carbon from carbonic acid in the presence 

 of sunlight and the liberation of oxygen. 

 This phycocyanin is probably set free in the 

 processes of putrefaction, and may be the 

 cause of the disagreeable effects noted above. 

 A very minute blue-green alga (Richelia 

 intracellularis) occurs within the cells of 

 Rhizosolenia, and apparently reproduces itself 

 inside the diatom cell. It is not yet known 

 how it penetrates into the diatom, but it 

 has been suggested that it probably does so 

 during an early stage in the life-history of 



