1 ('»(» T. F. SMITH ON DIATOM STRUCTURE. 



edge of the membrane and the other with it over the whole diatom. 

 This, I hope, will satisfy both class of objectors, as it meets the 

 points of each. 



EXPLANATION OF PLATE XV. 



Fig. 1. Coscinodiscus centralis. Central part. Outer membrane sup- 

 posed to be removed. 

 „ 2. Same diatom. Outer membrane only. 

 „ 3. Same diatom fragment. Inner layer only, with piece torn out 



of centre. 

 ,, 4. Same as Fig. 3, with torn outer membrane projecting over cavity 

 underneath. 

 Object glass used, Swift and Son's ^\ inch oil immersion and D. eye- 

 piece. Magnification about 1,400 diameters. 



