DIATOM MOTION. 77 



In view of all the above, it would indeed be of interest to 

 learn what supposed basis there could have been for the asser- 

 tion that diatoms do not move except in fairly strong light. 

 This claim continues periodically to be made, and wild theories 

 as to the nature of diatom motion take root and grow there- 

 from. But why base any theory on mere supposition, when 

 experimental facts are within easy reach ? For, as happens 

 in this case, the facts may turn out fatally in opposition to 

 the theory. 



