COMMUNITIES OF THE SEA BOTTOM 353 



sional phenomena in the faciations of the Balaniis-Littorina biome in 

 the enclosed Puget Sound waters (Shelford et al., 1935) had seemed 

 to offer a difficulty. These studies, however, were carried on only for 

 a short period, and the work of Hewatt (1935) on the Balanus-My- 

 tilus californianus association on the open shore over a long period has 

 demonstrated a clear succession. This fact, and the almost certain 

 occurrence of succession where bottom must develop, covers nearly all 

 the distribution phenomena of the bottom fauna to parallel those de- 

 scribed for plants and considered together on the surface of the land. 

 Since climax and succession have formed the natural basis for classi- 

 fication on land and promises to do so in the sea, the study of com- 

 munity development in connection with public works, especially those 

 in waters of high salinity, where new channels are opened and piers 

 built or dredging done, should be encouraged. The investigation of 

 successional changes in deeper waters is much more difficult but not 

 impossible. Pelagic communities in themselves, which appeared to 

 afford unusual difficulties as regards dominants, have gradually be- 

 come susceptible of analysis as knowledge has advanced, and study of 

 succession or invasion of denuded water is coming into the range of 

 the possible. 



