136 A STUDY OF WELK 



expels all fluids that it can with the obvious end result that the 

 organism's water-reserve is speedily lost, its water content sinks 

 swiftly to the danger point and, if desiccation continues, the 

 animal dies. 



Since this series provides a representative range in size 

 of the normal Buccinum population the average of these figures 

 should give a reliable picture of the water-loss of the animals. 

 When this average is calculated it is found that the average 

 rate of loss of water per hour expressed in terms of percentage 

 of initial total water content is as follows: for the first hour and 

 a third, 4.19 per cent per hour; from the end of the first hour 

 and a third to the end of two and a half hours, 3.55 per cent 

 per hour; from the end of two and a half hours to the end of 

 four hours 1.48 per cent per hour; from the end of four hours 

 to the end of six hours, 0.77 per cent per hour; from the end of 

 six hours to the end of eight hours and forty-five minutes, 0.51 

 per cent per hour; from the end of eight hours and forty-five 

 minutes to the end of twelve and a half hours, 0.23 per cent per 

 hour; from the end of twelve and a half hours to the end of 

 twenty-one hours and forty-five minutes, 0.24 per cent per hour. 

 Thus it is easily seen that the animals begin the dessication 

 period with a relatively enormous rate of water loss that brings 

 their reserve sharply downward to the danger point. Thus on 

 the average during the twenty-one hours and forty-five minutes 

 of desiccation the animals lost 18.07 per cent of their initial 

 total water content but when considered hour by hour this loss 

 shows an extraordinary and significant crowding of that loss 

 into the early period of exposure. Thus, considered in terms of 

 percentages of the entire water loss sustained, the animals lost 

 29 per cent during the first hour and a third of desiccation, 55 

 per cent during the first three hours and no less than 65 per cent 

 during the first four hours of the twenty-one hour period over 

 which water loss was taking place. During the last sixteen 

 hours of the twenty-one hours the loss is, in sharp contrast, 

 being only 16 per cent of the total loss that intervenes between 

 the beginning of the exposure and the death of the organism. 



