NOTES ON SOME PROBLEMS OF ADAPTATION: 8. 

 CONCERNING "MEMORY" IN ACTINIANS. 1 



W. J. CROZIER, 

 ZOOLOGICAL LABORATORY. RUTGERS COLLEGE. 



By a number of writers (cf. Parker, '17) it has been believed 

 that certain animals of intertidal habitat may continue for a 

 time to exhibit rhythmic movements, either of locomotion or of 

 opening and closing, when they have been removed to aquaria 

 and maintained under more or less constant conditions, and. 

 further, that such periodic movements may be synchronous with 

 the rise and fall of the tide. Unfortunately, many of the in- 

 stances brought forward, e.g., among the actinians, have been 

 found upon closer scrutiny to yield no real evidence of a persisting 

 "memory" of tidal events. 



One of the commoner Bermudian sea-anemones, the red Actinia 

 bermudensis Verr., occurs abundantly in caves along the shore 

 and in other mud-free situations open at times to a moderate 

 surf, but almost always between the tide lines. When the tide 

 falls, the actinians retract the tentacles and constrict the column- 

 sphincter. Commonly these sea-anemones hang upside down 

 from the under faces of stones, but they are also abundant upon 

 tiny ledges in the walls of small caves in any event, occurring 

 in situations such that they are rarely left in a tide pool, but are, 

 on the contrary, freely exposed to the atmosphere by the retreat- 

 ing tide. 



The much larger actinian Condylactis passiflora usually lives 

 beneath low tide, with the column imbedded among stones; at 

 extremely low tides, however, some individuals may be left a 

 little distance out of water, and it is noteworthy that these do 

 not retract the tentacles and contract the column, but instead 

 hang down limply with the tentacles extended and the column 

 passively stretched by the weight of the fluid in the interior 

 cavity. 



1 Contributions from the Bermuda Biological Station for Research, No. 134. 



117 



