370 SISTER MARGARET ANN 



but at midnight. This ability to be " re-set " constitutes an 

 advantageous adaptive characteristic for the species, making it 

 possible for the beginning time of the cycle to be varied in 

 harmony with changing physical conditions depending, for 

 example, on location. 



Besides rhythms of pigment change, still others were observed 

 correlated to the feeding habits of the fiddler crab. Among 

 these were the change in rate of oxygen consumption and in 

 running activities. With respect to the first, crabs and other 

 organisms kept in sealed respirometers showed a daily varia- 

 tion in oxygen consumption which coincided with the crab's 

 natural feeding times. With respect to the second, wires 

 attached to the legs of crabs contained in vessels of seawater 

 and connected to mechanical recording devices registered a 

 daily fluctuation in activity which coincided with the diurnal 

 and tidal running times of the free fiddler crabs on their native 

 beaches. 



Rhythms were likewise observed in such diverse organisms 

 of the plant kingdom as potatoes, carrots and the seaweed, 

 Fucus. Here, too, even when the humidity and barometric 

 pressure were considered to be successfully maintained at a 

 constant level by the experimenters, there continued to be 

 observed a regular pattern of increase and diminution in the 

 rate of oxygen consumption for a number of organisms. These 

 observations, more than any others, led to the formulation of 

 hypotheses indicating that some kind of " information," some 

 kind of stimulus, undetected by the observers, was getting 

 through to the isolated organisms. The possible roles of ioni- 

 zation of air and of various components of cosmic radiation as 

 transmitters of this " information " are now under investigation. 

 Recent work appears to offer something in the nature of sub- 

 stantiation of these explanations. 



This shift of attention to outside " information," outside 

 stimuli, marks an interesting new departure. In contrast to the 

 tendency to consider each organism as an isolated entity, it 

 suggests that outside stimuli, emanating (in the case of cosmic 



