3L8 J. DEBY ON THE STRUCTURE OF THE DIATOM VALVE. 



themselves by the examination of both recent and fossil slides in 

 my possession, and plates and photographs accompanying various 

 papers on the subject. I have full confidence that they will, after 

 such an examination, form a definite opinion, coinciding with my 

 own. It is very difficult and rather perilous to exhibit such 

 delicate subjects at a public meeting under a -^ or -^ inch objec- 

 tives, and for these reasons I should much prefer a private exhibit in 

 mv own studio. 



