The Microscope. 205 



THE MOTION OF DIATOMS. 



C. OUDERDONK, RUGBY, TENN. 



HAVING studied the Diatomaceae for a few years mainly in 

 regard to a discovery of their mode of motion, I have a few 

 suggestions to offer my co-workers, if so be, they are found wor- 

 thy a place in your journal. 



In studying the phenomena of the motion of those organs it 

 became obvious to me that the motion could not be caused by 

 cilia, nor by the flow of water in and out of the frustule. The 

 following facts became clearly established by continuous obser- 

 vation, viz : The motion is on the outside of the valves ; it is 

 from end to end, or with the long axis of the organism ; it is 

 rythmic, the motion is reversed at intervals ; it is not of the na- 

 ture of swimming, hence there can be no propelling organs in the 

 form of fins or motile cilia ; the diatomaceae can only move when 

 they come in contact with some substance more firm than them- 

 selves, if the contact is with lighter particles, the particles are 

 moved, not the diatoms; and further, the best glasses made fail 

 to show a trace of motile organs. This last fact is significant, 

 for it must be apparent to the thinking mind that organs of what- 

 ever nature, large enough to move a large pinularia, must, in the 

 nature of things, appear under a good wide-angled glass. 



In view of the facts enumerated I said there is a fluid in mo- 

 tion on the outer surface of the valves, no other supposition 

 will account for the observed phenomena. So I turned my at- 

 tention to the discovery of the fluid, or semi-fluid. 



I turned my attention to the Palmellacese. Here I had an 

 invisible frond, firm enough to be lifted out of the water and 

 hold the green globular masses contained in it. I began to search 

 for stains to make this invisible matter visible. I found that 

 methyl analine green stained the palmella a clear blue, while it 

 also hardened it. I found that this stain also stained the living 

 diatoms blue ; more than this my success was far beyond what 

 I had hoped for, for I saw in many cases a blue mantle slowly 

 unfold and detach itself from the now white, denuded frustule. 

 Subsequently, bv many observations, I have found that all dia- 

 toms which have come under my notice are encased in a gelatin- 

 ous pallium ; that this pallium is most manifest under the action 



