208 PROCEEDINGS OF THE ACADEMY OF [May-Oct., 



also; acicular species like Lichmophora and Climacosphenia shoot 

 out at many angles, thus leaving Arachnoidiscus and other sedentary 

 forms to bear the burden of growth-pressure. This intensive growth 

 pressure in the struggle for existence in the overcrowded sea-tene- 

 ment may be responsible for the many deformations of diatoms 

 and the forming of Arachnoidiscus ehrenbergii var. cuneatus. 



