40 Messrs Purvis and Warwick, The Influence , etc. 
These facts may be explained chemically ; for it is well known 
that the rays of high refrangibility have greater chemical energy 
than those of low refrangibility. It may be that the former 
instigate chemical changes within the cell antagonistic to the 
development of spores, whilst the latter, having much less 
chemical energy, have little or no influence, and the sporulation 
proceeds under healthier conditions. On the other hand, the 
retardation may be explained physically : for it may be that the 
vibratory motion of rays of high refrangibility shatters or neutra- 
lises that of the protoplasm of the cells which would result in 
the formation of spores, whilst the rays of low refrangibility are 
unable to exert such an influence. 
The investigations will be continued and particularly with 
regard to the ultra-red and ultra-violet rays. 
