106 



C. M. CHILD 



representing a certain fraction of the total body length may 

 be the anterior region of one of the posterior zooids in one case, 

 the posterior region in another, and in still others may include 

 parts of two different zooids and its constitution in these re- 

 spects is a factor in determining the character of its head. 



In the present section the important points of each series 

 and certain differences and resemblances between different 

 series are briefly noted. The general conclusions and their 

 interpretation are reserved for the following section. For the 

 sake of brevity, a change in the head-frequency toward the 

 'headless end of the series is termed a downward shift a change 

 toward the normal end, an upward shift in head-frequency. 



Series 512, table 1, shows the effect on head-frequency in | 

 pieces (a-f, fig. 8) of twenty-four hours in KCN of two differ- 

 ent concentrations. In the control I a-f the head-frequency 



TABLE 1 

 Series 512. Worvis 16-17 mm., in laboratory seven months and twenty days before 

 experiment. I. Control in water; II. Each piece as soon as cut in KCN mj 200000 

 for twenty-four hours; III. Forty pieces; each piece as soon as cut in KCN m/50000 

 for twenty-four hours 



