RHYTHMS IN BEHAVIOR 157 
the spray from the incoming tide begins to moisten them 
they emerge and begin crawling about. Their phototaxis 
changes with the tide, becoming negative when the tide 
is high and positive when it is low. Bohn placed Littorina 
in an aquarium and found that for several days they under- 
went changes in their phototactic responses parallel with 
those of specimens upon the rocks. Similar experiments 
have been made by Morse on a species of Littorina on the 
New England coast, but he failed to obtain any evidence 
of a tidal rhythm. And more recently Haseman has in- 
vestigated the tidal rhythms of several species of Littorina, 
none of which showed any rythmical movements independ- 
ent of the direct influence of the tides. 
Among actinians Bohn has found in many cases daily 
rhythms due to the alternation of light and darkness super- 
posed upon tidal rhythms. Both of these rhythms are 
influenced greatly by the nature of the habitat in which the 
anemones live. Individuals situated rather high upon the 
rocks and living therefore under strongly contrasted con- 
ditions in high and in low tide exhibit tidal rhythms to a 
marked degree; whereas those which live at depths in which 
they are little affected by the waves show little or no in- 
fluence of the tide. Alternation of day and night affects 
anemones to a greater or less degree in all habitats; its 
influence is complicated by many factors, such as degree of 
exposure to the sun, depth of water, shock of waves, tem- 
perature, purity of the water, and various other causes. 
The daily rhythms differ greatly in anemones from different 
local situations, according to the influences to which the 
animals are adapted. These rhythms with their various 
characteristics peculiar to different habitats were found to 
persist for several days in aquaria, but they gradually wore 
away. 
