IO MARIE A. HIXRICHS. 



which in order that it may be absorbed and so become effective, 

 must have, (B~) a wave-length range including that of the absorp- 

 tion band of the particular sensitizer used. 



2. The susceptibility to visible radiation following sensitization 

 with the following sensitizing dyes (eosin, benzoflavine, neutral 

 red, and methylene blue) is differential, i.e., regions of high 

 physiological activity are first to be modified in their develop- 

 ment. Differential inhibition, recovery, and acclimation have 

 been produced in this way. 



3. It is possible to produce these effects (as with Fundnlus and 

 ultraviolet radiation) by exposure during the first few minutes 

 after fertilization, indicating an early difference in susceptibility 

 of various regions of the egg. Differential modification is also 

 obtained by fertilizing normal eggs with photodynamically 

 treated sperm. 



4. These experiments confirm the view of the nonspecific and 

 quantitative nature of susceptibility relations along the body 

 axis. 



I wish to thank Dr. Ralph Lillie of the Dept. of Physiology; for 

 his cooperation in the working out of this problem. Acknowl- 

 edgment is also due to Dr. C. M. Child of the Dept.- of Zoology, 

 and to Dr. S. E. Pond of the Dept. of Physiology, Washington 

 University Medical School, for helpful suggestions. 



LITERATURE CITED. 

 Baldwin, W. M. 



'15 The Action of Ultraviolet upon the Frog's Egg. Anat. Rec., Vol. 9, pp. 



365-381. 

 Bayliss, W. M. 



'20 Principles of General Physiology. London. 

 Bohn, G., and Drzewina, A. 



'23 Action toxique du rouge neutre en presence de la lumiere. C. rend. Soc. 



Biol., Vol. 89, No. 24, pp. 386-388. 

 Bovie, W. T. 



'13 Sensitization of Albumin and Paramcecium to Heat. Science, Vol. 37, 



PP- 373-375- 

 Bovie, W. T., and Klein, A. 



'18 Sensitization to Heat Due to Exposure to Light of Short Wave-lengths. 



Jour. Gen. Physiol., Vol. i. pp. 331-336. 

 Bovie, W. T., and Barr, C. E. 



'24 Photocytolysis as a Measure of Metabolic Activity. Science, Vol. 59, No. 

 1514, p. 22. 



