THE RELATIVE PHYSIOLOGICAL EFFECTS OF /3- AND 

 7-RAYS UPON THE EGG OF NEREIS. 



By ALFRED C. REDFIELD and ELIZABETH M. BRIGHT. 



{From the Laboratory of Physiology, Harvard Medical School, Boston, and the Marine 

 Biological Laboratory, Woods Hole) 



(Received for publication, June 17, 1919.) 



As a preliminary to an investigation of the relative effects of /3-rays 

 of different velocities upon the egg of the marine worm, Nereis lim- 

 bata, it is desirable to determine how far the reaction in question is 

 due to the ^- and to the 7-rays.^ This information is also of impor- 

 tance in connection with a recently pubhshed^ determination of the 

 temperature coefficient of the action of the rays from radium upon 

 these eggs since, as will be seen, it enables us to assign this coefficient 

 to the action of the jS-rays. 



When unfertiHzed Nereis eggs are exposed to radiations from ra- 

 dium and then fertilized, the fertilization membrane which results is 

 of unusual thickness.^ We have shown that this reaction may be 

 made to serve as a measure of radioactivity since a simple relation 

 exists between the volume of the membrane formed by the eggs and 

 the intensity of the radiation to which they have been exposed.'* 

 When used in this way the Nereis egg will give a measure of the in- 

 tensity of the rays only in as far as they are physiologically effective. 

 Our method has consisted in exposing a series of eggs for uniform 

 periods of time to radiations passing through various thicknesses of 

 aluminium and in determining the resulting membrane volumes. At 

 the same time a series of eggs from the same female worm was ex- 

 posed to various known intensities of radiation, produced by varying 

 the distance between the eggs and the source of radiation, and evalu- 



1 Redfield, A. C, and Bright, E. M., /. Gen. Physiol., 1919-20, ii, 31. 



2 Redfield, A. C, and Bright, E. M., /. Gen. Physiol., 1918-19, i, 255. 

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



^ Redfield, A. C, and Bright, E. M., Am. J. Physiol, 1917-18, xlv, 374. 



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