DYNAMICS OF MORPHOGENESIS 173 



In the tadpole the concentration of the narcotic in the central 

 nervous system may be greater than in other parts of the body, 

 but there is no evidence that this is the case in Planaria. The 

 assumption of the universal importance of the coefficient of dis- 

 tribution in the action of narcotics is not justified from experi- 

 mentation of higher animals alone. 



Meyer found that the coefficient of distribution of alcohol 

 between water and olive oil almost doubled with a rise of temper- 

 ature from 3° to 30°C., i.e., a change of 27°. For a change of 10° 

 in temperature the change in the coefficient would then be com- 

 paratively slight. This brings us at once to the question whether 

 the change in the coefficient of distribution with change in tem- 

 perature is sufficient to account for the observed differences 

 in physiological resistance. If we find that the differences in 

 physiological resistance of two similar lots of planarians at tem- 

 peratures 5° or 10° apart are considerable, we must at least admit 

 the probability that the coefficient of distribution is not the only 

 and perhaps not the most important factor involved. The two 

 following series show the character of results obtained with alcohol 

 by the direct method. 



Series 561. Worms 18 to 20 mm. in length from same stock. 

 Lot 1, ten worms in alcohol 5 per cent at temperature of 20° to 21°C. 

 Lot 2, ten worms in alcohol 5 per cent at temperature of 10° to 

 11°C. 



Worms in alcohol 11.00 a.m., October 29, 1912. Observations 

 were made every half-hour but only alternate observations are 

 given in the table. 



Table 3 shows that Lot 1 at the higher temperature begins to 

 disintegrate first and disintegrates much more rapidly than Lot 

 2 at the lower. In Lot 1 disintegration begins after three hours, 

 in Lot 2 it begins in one worm after five hours, but not until 

 after nine hours in the others. In the single case in this lot where 

 disintegration began after five hours it remained localized in a 

 very small area on the preocular region of the head and did not 

 begin to advance further until after nine hours. Undoubtedly 

 this region was a region of high rate of reaction resulting from 

 some slight injury in handling the worms. It is possible to induce 



