256 TEMPERATURE COEFFICIENT OF /3-RAYS 



constant. Osterhout and Haas,^ who likewise obtain a high value, 

 1.81, for the temperature coefficient of photosynthesis, attribute it 

 to the fact that they are dealing with a series of catenary reactions, 

 of which the determining member is not a true photochemical process. 



The development of a method of measuring the physiological 

 action of radiations from radium has enabled us to determine the 

 effect of temperature upon this process with precision. This method 

 depends upon the fact, first observed by Packard,^ that the fertiliza- 

 tion membrane of the egg of the marine worm, Nereis, is greatly en- 

 larged if the eggs have been exposed to radium prior to fertilization. 

 We have shown® that the extent of this change is a reliable measure 

 of the intensity of radiation and time of exposure. Our problem 

 has been to determine what effect the temperature at which radia- 

 tion takes place has upon the velocity of the reaction under uniform 

 intensity. 



To this end a few drops of Nereis eggs were placed in the bottom 

 of a test-tube and this was inserted into a vessel containing chopped 

 ice and allowed to stand until it had taken on the temperature of the 

 ice. A tube of radium emanation was then suspended above the 

 eggs. As radiation proceeded, a few eggs were withdrawn from time 

 to time, placed in sea water at room temperature, fertilized, and the 

 thickness of the membranes was measured after a uniform period of 

 time. A second lot of eggs from the same female was then treated in 

 exactly the same way, except that during radiation the test-tube 

 containing them was placed in a thermos flask filled with water at 

 room temperature. 



The exposure of unfertilized eggs to these temperatures, without 

 radiation, does not affect the volume of the membrane which is formed 

 upon fertilization, although somewhat higher temperatures may be 

 expected to cause an enlargement of this structure.^ 



This procedure possesses the advantage that the two lots of eggs 

 are kept at different temperatures only during the period of radia- 

 tion, during which no visible change occurs in these cells. The proc- 



^ Osterhout, W. J. V., and Haas, A. R. C, /. Gen. Physiol., 1918-19, i, 295. 

 5 Packard, C, /. Exp. ZooL, 1915, xix, 323. 



«Redfield, A. C, and Bright, E. M., Am. J. Physiol., 1918, xlv, 374. 

 'Just, E. E., Biol. Bull., 1915, xxviii, 1. 



