392 



G. H. PARKER 



ings could be obtained from each sucker. As it was the object of 

 this investigation to ascertain the maximum capacity of each 

 sucker, the highest breaking force among the four or five observed 

 was taken rather than an average. 



The faces of the suckers in Octopus are very regularly circular 

 and after each test the diameter of the given sucker was measured 

 in millimeters. From these diameters the areas of suction of 

 the several suckers were calculated in square millimeters. The 

 theoretical maximum suction for each such area was then worked 

 out on the assumption that an atmosphere is equal to 1.033 kilo- 



TABLE 1 



Diameters of suction areas {millimeters) , calculated areas of suction {square milli- 

 meters), breaking forces {grams), theoretical maximum suction {grams), and 

 percentages of efficiency for eight suckers from the arms of Octopus bimaculatus 



Observed diameters of 

 suction areas in mm 



Calculated areas of suc- 

 tion in sq. mm 



Observed breaking forces 

 in grams 



Theoretical maximum 

 suction in grams 



Efficiency in percentages.. 



6.0 



28.27 



147.4 



292.0 

 50 



grams per square centimeter. These derived results together 

 with the original observations are brought together in table 1. 

 In table 1 the suckers have been arranged in the order of size 

 from smallest to largest. The smallest one shows the smallest 

 breaking force, 29.2 grams, and the largest one the largest, 

 147.4 grams, the others forming a series between these two 

 extremes. This series, however, does not conform very closely 

 to the series of theoretical maximum suctions calculated for the 

 series of suckers on the basis of atmospheric pressure. The 

 relation of these two series is more easily understood from the 

 plottings in figure 1 than from the numbers in table 1. The 



