THE A.MERICAN MO^ttHLY 



[Jannarv, 



Motion of Diatoms. 



The article in the last Journal 

 from Dr. Geo. M. Sternberg, con- 

 firming Dr. Wallich's view relative to 

 the motion of Diatoms, is interesting 

 to all who have studied the subject. 

 He says : " Dr. Wallich ascribes 

 these motions to the existence of pre- 

 hensile filaments capable of alternate 

 extension and retraction, of extreme 

 tenuity, yet of extraordinary strength 

 and elasticity." Dr. Sternberg has 

 not been able to see these filaments 

 in living diatoms, and therefore can- 

 not verify the assertion. His method 

 of instantly terminating the life of di- 

 atoms is both interesting and unique ; 

 but, judging from the instantaneous 

 contraction which has taken place in 

 the many animal and vegetable ob- 

 jects which I have attempted to pre- 

 pare for mounting, I am surprised 

 that he succeeded so well. About 

 eight years ago I was in correspond- 

 ence with Prof. H. L. Smith concern- 

 ing the motion of diatoms, when he 

 called my attention to certain filamen- 

 tous growths, hairs, or pseudopodia, 

 long and very slender, proceeding from 

 the edge of Stephanodiscus Niagarce.. 

 Sometimes they were twice as long as 

 the diameter of the diatom. No one 

 had seen them but himself at that 

 time, and he had only observed them 

 two or three times. In a few weeks 

 I was gratified by finding the same 

 attachments in a gathering which I 

 made from the water-supply from Ni- 

 agara River. 



I still have some of them mounted 

 on a slide which shows them very 

 distinctly. In 1876 I sent the slide, 

 with others, to microscopists for their 

 examination and opinion as to the 

 nature of the filaments. Those of 

 them who ventured an opinion were 

 inclined to consider them pseudopo- 

 dia. I quote from one correspond- 

 ent, Mr. Geo. W. Morehouse, who 

 says : " Certainly there is strong re- 

 semblance to pseudopodia. Did you 

 detect any motion of the pseudopo- 

 dia while the diatoms were living ? 



* * * On 'the whole the resem- 

 blance to pseudopodia is greater than 

 to anything I know of. Plants do not 

 possess true pseudopodia, but, in the 

 lower forms, are there not some fami- 

 lies of plant-animals, possessing some 

 characteristic ofboth animal and plant? 

 Is it possible in all cases to distinguish 

 between protoplasm and sarcode ? 

 * * * I consider your dis- 

 covery of considerable importance, 

 and hope you will give the facts to 

 the public." I have not done this, 

 except as above indicated and also by 

 showing the slide to a few individu- 

 als. I have been waiting for more 

 light. Now, if Dr. Wallich and Dr. 

 Sternberg have been able to photo- 

 graph or prepare diatoms in any 

 other way, showing any indications of 

 these filaments, whether prehensile or 

 not, it would give me great pleasure 

 to have an opportunity to compare 

 their specimens with mine. For my 

 own part, I have been inclined to 

 regard the filaments as a parasitic 

 fungus, but this may be far from the 

 truth. There is one fact, however, 

 that must be borne in mind, viz. : 

 that Stephanodiscus^ like all the dis- 

 coidal diatoms, has very little mo- 

 tion, if any. Then, what are the fila- 

 ments for, if they are a part of the 

 diatom ? I have observed another 

 point of great interest in the study of 

 this subject, and it may ultimately 

 help to throw light on it. In my con- 

 tinued examination of the diatoms 

 found in the Niagara water-supply, I 

 have at times found the smaller dis- 

 coidal diatoms, such as Orthosira, 

 Melosira, and some of the genus Cy- 

 clotella, in great abundance. These 

 were stationary, of course; but on the 

 slide, under the cover-glass or not, 

 they would repel every light-body, 

 and all the debris from contact with 

 them, so that a distinct annulus, clear 

 and well defined, would be formed 

 around them. The width of the an- 

 nulus was about equal to the diame- 

 ter of the frustule. This phenome- 

 non may be witnessed by any Avho 

 are so fortunate as to collect this 



