CONTROL OF HEAD FORMATION IN PLANARIA 33 
of the controls, but thereafter the controls and the pieces in the 
chloretone solution lose weight at the same rate (six experiments). 
In mol. 1/3000 chloroform the rate of oxygen consumption of 
the pieces rises slightly above that of the controls sometime 
after the fourth day and remains slightly above during the two 
weeks' record. The loss of weight of the pieces in chloroform is 
slightly greater during the first three days, but during the later 
period of regeneration takes place at the same rate as in the con- 
trols (six experiments). In the one concentration of ether em- 
ployed, mol. 1/300, the rate of oxygen consumption and loss of 
weight of the pieces is approximately the same in both controls 
and in the pieces subjected to the ether solution throughout the 
entire period of two weeks (six experiments). 
These results are somewhat similar to those recorded by others. 
Winterstein ('14) found that the oxygen consumption of the 
spinal cord of the frog was increased during alcohol narcosis. 
Vernon ('12) found that weak solutions of narcotics increase the 
oxygen consumption of isolated tissues. Tashiro and Adams 
('14) found that weak solutions of urethane and chloral hydrate 
increase the carbon-dioxide production of nerve fiber. Win- 
terstein ('19) records that Elfving found that the carbon-dioxide 
production of Salix leaves was increased in certain environments 
of dilute ether and chloroform. Winterstein also records that 
von Lauren, Markovine, Kosinski, Gerber, and Zaleski, and 
others have found that weak solutions of narcotics increase the 
rate of respiration of plant cells. 
DISCUSSION 
If head frequency in A pieces is decreased and in C pieces 
increased by reason of exposure of the pieces for the same period 
of time to the same concentrations of the same anesthetic, and the 
head frequency of the B pieces is not altered, or is increased or 
decreased depending on the length of the period of exposure and 
the concentration employed, it follows that there must be some 
difference between the effects of the anesthetic on the three sets 
of pieces. In analyzing the nature of this difference, we shall 
consider the possibilities in the A and C pieces, since the effects 
