AND INHERITANCE IN PEDIASTRUM. 



419 



TABLE VII. 



Frequencies of the Angles of Values between the Extreme 86° and 176° 



IN A Series of Thirteen Colonies of P. Boryanum taken by Chance. 



The Values are Grouped by Threes. 



120° is 252. The total number which have a value less than 120° 

 is 189. The number recorded for 120° is perhaps unduly large. 

 Since, as I have noted, it is quite impossible to judge within one or 

 two degrees with any certainty there is perhaps a tendency to assign 

 too frequently an angle of 120° rather than 119° or 121°. On the 

 other hand, it is not impossible that the angle 120° being the point 

 of equilibrium in the surface tension group, there may be some 

 especial fixity in the configuration when it is once achieved, so that 

 when it arises by chance as a result of the more protracted slow 

 writhing movements of the final stage in forming the colony, it may 

 be maintained in a certain number of points of intersection at the 

 expense even of greater inequalities at other adjacent points. When 

 once attained exactly it may be more persistent than any other angu- 

 lar value. But w^iether or not the number of angles with a value 

 of 120° is correctly determined there is no question as to the general 

 tendency in these angles to fluctuate about 120° as a center or modal 

 point. On the other hand, it would be quite inadmissible in the light 

 of the results obtained by comparing the corresponding angles of a 

 series of colonies with similar arrangement (Table V.) or a single 

 colony selected for its symmetry ('16, p. 98) to conclude that the 

 type colony of P. Boryanum should have all its included angles 

 equal to 120°. With sufficiently large numbers of cases the sec- 

 ondary modal points representing the special values of the included 

 angles of the central cell, etc., should emerge. 



The average values for the corresponding sides of the cells in 



