CONTROL OF HEAD FORMATION IN PLANARIA 



23 



inhibition of stimulation and not necessarily a true measure of 

 the degree of inhibition. 



Ether 



Head frequency. The least and greatest effects on head fre- 

 quency obtained by subjecting the pieces to various concentra- 

 tions of ether for short periods after section are given in table 3A. 



TABLE 3A 

 Head freqvency — ether. In per cent 



8/24, '20. 16- to 18-mm. worms. Fed 24 hrs. before cutting 



2/3, '21. 14- to 16-mm. worms. Fed two weeks before cutting 



Control. 



2. M.1/20. 



All other results fall between these two extremes. Eight experi- 

 ments were carried out, and the results in general did not differ 

 greatly from those obtained with chloretone and chloroform. 

 They require no extended comment. The increases in head 

 frequency in the B pieces in almost all cases and the failure to 

 obtain marked decreases in the A pieces and any decreases what- 

 ever in the B pieces indicate, as in chloroform, that the effect of 

 the ether is relatively greater on the nervous stimulation of the 

 Y region than its effect on the general protoplasmic activity of 

 the X region. 



