CONTROL OF HEAD FORMATION IN PLANARIA 15 



The measurement of the oxygen consumption of pieces from 

 all three levels in bulk obviously does not afford any comparison 

 of the effect of the anesthetics on the stimulation bj^ section of 

 pieces from different levels of the gradient. But it is known 

 that anterior pieces are less stimulated than posterior and the 

 measurement of the effect of the anesthetics on the stimulation 

 of section in all pieces is quite satisfactory for the purpose of 

 analyzing the factors concerned in head determination. 



After the data on the oxygen content of the original stock 

 solutions and water and of the liquids in the flasks had been 

 secured, the pieces were weighed. The method of weighing was 

 as follows : The pieces were poured into a funnel lined with hard- 

 surfaced filter-paper. The liquid was then poured off and the 

 filter-paper removed and drawn over a dry glass plate until it 

 adhered firmly. The pieces w^ere then picked up with a thin 

 spatula and placed in a Paar w^eighing tube, the cover of the 

 tube replaced, and the tube with its contents weighed, the weight 

 of the tube being known. It is admittedly unavoidable not to 

 weigh some of the liquid bj- this method, but it is more important 

 to avoid excessive drying in experiments involving tests of oxy- 

 gen consumption at intervals throughout the period of regenera- 

 tion. Even with this method there was no doubt some slight 

 stimulation resulting from partial drying and handling. The 

 results were consistent, however. In comparable experiments 

 pieces lost weight at the same rate during the period of regenera- 

 tion. Worms of the same physiological condition showed the 

 same rate of oxygen consumption per unit of weight. It seems, 

 therefore, that the error introduced by w^eighing a small amount 

 of the liquid with the pieces was fairly constant. 



EFFECT OF STRONG SOLUTIONS ACTING FOR SHORT PERIODS 



AFTER SECTION 



Chloretone 



Head frequency. The data obtained on the head frequency of 

 pieces subjected for short periods after section to various con- 

 centrations of chloretone are given complete in table lA. These 



