THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL 



Vol. IV. 



Boston, April, 1883. 



No. 4. 



The Movement of Diatoms. 



BY CORNELIUS ONDERDONK. 



Noticing that the motion of the 

 diatomacete is attracting attention at 

 this time, I desire to publish a few 

 words preliminary to a more complete 

 memoir on my own discoveries con- 

 cerning the subject, having directed 

 my attention to the motion of the dia- 

 toms during the past five years. 



I'he motion of diatoms is caused by 

 what I will call the \wo\X\^ pall i urn — 

 a gelatinous, invisible envelope, that 

 entirely envelopes the diatom in the 

 case of the strong-moving naviculae, 

 but only partially in the case of 

 other forms of weaker motion. 

 This is no mere theory, though I had 

 worked out the theory long before I 

 succeeded in making the pallium 

 plainly visible, and turned my whole 

 attention to staining the motile matter 

 long before I saw a trace of it. I 

 have at length succeeded in staining, 

 hardening, and detaching the pallium, 

 and I now have many of them mounted, 

 also many diatoms, in all stages of 

 disrobement, if I may use the term. 

 The pallium is folded to the diatom in 

 many minute currugations. Under 

 the action of the reagent, the minute 

 currugations slowly begin to expand 

 out from the diatom like pseudopodia; 

 longer and longer they grow, but soon 

 we see they are not pseudopodia, for 

 they straighten out into a membrane. 

 The unfolding mantle splits along the 

 midrib, and, in some cases, leaves the 

 flinty shell. This is not the mem- 

 brane spoken of as investing the dia- 

 toms by many investigators, as this is 

 at once destroyed by alcohol or acids. 

 The same reagent reveals a similar 



envelope on the oscillaria; and I be- 

 lieve the motion to be the same in the 

 two forms of protophytes. In fact, if 

 a diatom was a long elastic rod, it 

 would merely vibrate, for I have ob- 

 served that the motion is generally in 

 opposite directions on the two valves ; 

 but the diatom can only move by 

 creeping along a surface, hence, its 

 motion is only affected by the direc- 

 tion of the motion of the gelatine on 

 one valve — the one that comes in con- 

 tact with a surface. The motion is 

 only on the sides, or valves. If a 

 frustule is turned with its so-called 

 front view up, it cannot move, at least 

 those under my investigation did not, 

 unless one of the valves comes in con- 

 tact with some body of greater weight 

 than itself, if we may so put it ; for 

 small particles will move along the 

 valves, while the diatom remains sta- 

 tionary. The ribs have much to do 

 with this power to creep, for the pal- 

 lium is folded to the ribs and being 

 striated length-wise, it is plain to see 

 how the pallium covers the valves 

 with thousands of little feet. There 

 is great room here for investigation 

 with the recent very wide angled 

 glasses, but let me here give common 

 glasses their due, for all that I have 

 discovered has been done with only 

 such. 



I will, when I can find the time, 

 publish the modus operandi for reveal- 

 ing the pallium. 



[It is to be regretted that the author 

 of the above article has not given his 

 method of observation, at least in out- 

 line. It cannot b3 expected that his 

 statements will receive much credence 

 in their present form. It is for us to 

 give to the world the results of original 



