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THE BIOLOGY OF HYDRA : 1961 



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CONTROL 500R 2 KR 5KR 25KR 50KR lOOKR 200KR 



DAYS OF AGE 



Fig. 15. Distribution of ages at death of Campanularia hydranths of 

 various ages after exposure to various dosages of X-rays. The highest peak 

 represents 23 hydranths. 



the two hour period which we used, it may be that there is a com- 

 plete arrest of metabohc activity inckiding the synthesis of the lytic 

 enzymes. 



It was current doctrine about two years ago that high energy 

 radiation is analogous to time in its effect on aging. We therefore 

 undertook to see whether Campanularia is aged by high doses of 

 radiation. We gave dosages up to 200,000 r and then followed the 

 longevity of individual hydranths. Figure 15 shows the average life 

 time at various dosages. The mean life time, under the control 

 conditions, was about 2.7 days, whereas at 100,000 r the average 

 life time was about 6.3 days. This radiation dose more than doubles 

 the longevity of the hydranth! 



Another remarkable fact is that hydranths continue to differen- 

 tiate and be initiated even one week after exposure although the 

 colony eventually dies. Figure 16 shows the survival curves of these 



