244 Marhings on the Pleurosigma angulatum. [SSIl ApX'^K 
Mr. E. Beck corroborated tMs view of the Lepisma scale by means 
of the binocular microscope. It is quite possible that the markings 
seen on other diatoms than the Angulatum may not all be on one 
surface. The markings on diatoms, and especially those on the 
P. angulatum have been the subjects of much discussion amongst 
microscopists. At the present time differences of opinion exist on 
this point. 
