306 



Hubert P. Yockey 



Wood's survivorship curves for thermal killing in yeast (25) are also given 

 in Fig. 4. The term in X^ again substantially represents the behavior of the 

 survivorship curve. The curve retains its form when the temperature is changed. 

 The -f- test shows in each case a very poor fit to A" but this presumably reflects 



Table I. Goodness of Fit for Wood's X-rav Survival of Diploid Yeast 



* 7 degrees of freedom 



the existence of small higher order terms as in the x-ray case. Attention is also 

 called to the aging of the grain beetle Calandra oryzae at 32.3°C and at 29. TC 

 shown in Fig. 2. The survivorship curve again retains the same shape, changing 

 only the coefficient of A^. 



The sensitization to thermal killing of Paramecium caudatum following 

 x-irradiation was first reported by Giese and Heath (42). They found a slow 

 recovery eff'ect, requiring several days. This parallels the earlier discovery of 

 Giese and Grossman (43) of sensitization to thermal killing by ultraviolet and 

 by visible light in the presence of photodynamic dyes (44). 



Baldwin (45) has pointed out the similarities between thermal killing and 

 killing by x-rays for the hymenopterous insect Dahlbominus fuscipennis. The 

 immediate consequence of both insults is a coma from which the insect may 

 recover to die later of delayed eflFects. Aging decreases the tolerance for both 

 temperature and x-rays. The dose-survivorship curve is not given accurately 

 but it has roughly the same shape for each agent. The diploid females are more 

 resistant than the haploid males. These observations parallel those of Wood 

 on yeast. 



It was mentioned briefly in the section on haploid organisms that Nybom 

 (27) has reported sigmoid x-ray survival curves for three species of green 

 algae, Chlamydomonas eugametas, C. Moewusii, and C. rcinhardi. Jacobson (28) 

 has studied C reinhardi in some detail and shows that the x-ray survivorship 

 curve fits accurately an equation of the foitn of equation (9). He points out 

 that this can 'be explained by a redundancy of genetic information.' Clark 

 and Herr (46) irradiated the haploid male and diploid female of Habrobracon 



