HOWARD B. NEVVCOMBE 



of the cells, the nuclei being clearly visible in a lightly stained cytoplasm, 

 whereas with continuous incubation the stainable material nearly filled 

 the cell. 



Table VII. — Effect on X-ray mutability of amount of air available during preliminary growth 



f X-ray dose 16min at 50 cm) 



* For unirradiated controls, size of inoculum, other treatments, and amount of growth see Table f 7. 

 Per cent survival = 73 -7, 58 •2, 61 -2, 70- 1, 69-4, 78-5, 66-7, 69-8, respectively. 



In a second experiment, spores were grown into somewhat longer strands, 

 having lengths of about thirty times their own diameter and probably 

 containing in the vicinity of thirty nuclei. The spores were incubated 

 intermittently, that is for 7 hours each day up to a total of 35 hours, 



Table VIII. — Effect on ultraviolet mutability of continuous versus intermittent incubation during 



preliminary growth 



* For unirradiated controls, size of inoculum, other treatments, and amount of growth, see Tabic 17. 



Per cent survival = 64-3, 66-5, 79-5, 99-7, 100, 92-5, 80-4, 86-0, respectively. 



J\fote : With intermittent incubation, the nuclei were small and clearly stainable, whereas 

 with continuous incubation, the cytoplasm seemed divided into large deeply staining bodies 

 which nearly filled the mycelial thread. 



335 



