CONTROL OF HEAD FORMATION IN PLANARIA 



21 



with chloretone. In exposures up to thirty-two hours there were 

 no decreases in head frequency in B pieces, even when the con- 

 centration and time of exposure were very nearly lethal. These 

 results indicate the greater effect of the chloroform on the stimu- 

 lation of the Y region as compared with its effect on the cells 

 of the X region. 



TABLE 2A 



Head frequency — chloroform. In per cent 



4/11, '16. 12-mm. worms. Fed six days before cutting 



2/5, '21. 14- to 16-mm. worms. Fed two weeks before cutting 



Oxygen consumptioji. Table 2B gives the high and low ex- 

 tremes of results obtained in measuring the rate of oxygen con- 

 sumption of pieces placed in suitable concentrations of chloro- 

 form immediately after section. The usual rate of oxygen 

 consumption of whole animals of the size and condition of 

 those used in table 2B is 0.00040 to 0.00045 cc. per milligram per 

 two hours. It will be be noted that the pieces subjected to the 

 chloroform have a rate very closely approximating that of intact 

 animals. This was true in all the nine experiments carried 

 out. 



