BIOTIC STRUCTURE AND BIOTIC ENERGY 15 



The most remarkable fact, in addition to this well-marked 

 rhythm of activity and repose, is that it continues apparently until 

 the death of the tiny organisms, although the organisms are kept 

 in complete darkness throughout the entire period of the captivity. 

 The number of flashing points diminishes nightly, at first very 

 rapidly, as the organisms are devoured for food by other creatures or 

 perish from various causes; but I have succeeded in observing the 

 recurrence of flashing at nightfall for twelve successive nights, at 

 the end of which period of captivity nearly all the organisms had 

 succumbed. 



Similar diurnal rhythmic change has been observed for shorter 

 periods in plant leaves, which alter their orientation in light and 

 darkness when the plants have been kept in continuous darkness. 



In the above instances we have examples of phasic activity timed 

 to a regularly recurring stimulus, but see that in the absence of that 

 stimulus there is something latent in the nature of the balanced 

 chemical activities of the colloids and crystalloids which leads to 

 phasic discharge and recuperation. For example, the phosphores- 

 cence is in all probability due to a phosphorescent secretion from a 

 gland. This gland has been timed by its development and environ- 

 ment so as to load itself up to discharging- point during the day, 

 and to be fired of? as the light recedes in the evening. The colloidal 

 constituents of the gland and their associated crystalloids possess 

 such a chemical constitution and physical aggregation that they run 

 their reaction of building up or synthesising the secretion at such 

 a rate, that the secreting cell after the lapse of the hours of daylight 

 will be charged up to a certain osmotic pressure with the phos- 

 phorescent secretion, either free in the cell or loosely united to the 

 producing colloids. Now this concentration is the potential factor 

 of the energy tending to force a discharge, and just as a Leyden jar 

 will discharge as the electrical potential passes a certain maximum 

 point and spark over, so the cell contents disrupt. The phos- 

 phorescent material if bound to colloid is set free and then discharged, 

 or if already free is discharged from the cell, and in this way 

 osmotic pressure is lowered and the cell's discharging power is 

 for the time spent, so leading to the opposite phase of rest and 

 recuperation. 



The typical histological changes accompanying the periodic 

 charging and discharging of the digestive glands are further examples 

 of alternating rhythm. During rest chemical changes occur, having 



