1882.J 



MICROSCOPICAL JOURNAL. 



43 



The Motion of Diatoms. 



BY C. M. VORCE, F.R.M.S. 



It is with great pleasure that I ob- 

 serve the awakening of interest in 

 this phenomenon. Like many others, 

 I have watched faithfully the curious 

 movements of the diatoms, in the ef- 

 fort to learn the means by which they 

 are accomplished, but up to this time 

 I have not been able to satisfactorily 

 account for them on any theory I 

 have yet heard of, so that I am still 

 in the very unsatisfactory predica- 

 ment of being unsatisfied with any of 

 the theories advanced by others, yet 

 having none of my own. 



However, I have accumulated quite 

 an array of facts bearing on the sub- 

 ject, and it seems to me that with the 

 objectives now to be obtained, the 

 solution of the mystery concerning 

 this motion may yet be accomplished 

 by some persevering observer. There- 

 fore, I offer the facts I have observed 

 in the hope that they may aid, in 

 some degree, to develop the truth. 



I have observed positive movement 

 in the following diatoms: Amphiprora 

 ornata, Nitzschia sigmoidea, Nitzschia 

 sp., Synedra sp., Surirella turgida Su- 

 rirellabiseriata, Surirella splendida (/), 

 Cymatopleura solea, C. Hibernica, Cym- 

 bella ciispidata, Navicula cryplocephala, 

 JV. cuspidata, Finnularia viridis; and 

 apparent movement in Stephanodiscus 

 NiagarcB, in a Gonphonema, and in 

 Cymatopleura elliptica. Also I have seen 

 detached valves, free of endochrome, 

 exhibiting apparently voluntary 

 motion which, it is obvious, must have 

 been caused by some force foreign to 

 the diatom. Most of my observations 

 have been made on fresh filterings 

 from the water of Lake Erie, in which 

 a large amount of flocculent matter 

 was present, and in which infusorial 

 life was abundant. 



The common phenomena of the 

 motion of diatoms are well described 

 by the Hon. J. D. Cox, in this Jour- 

 nal of April 1 88 1, p. 66, and may al- 

 ways be seen in a gathering of dia- 

 toms where much light matter is pre- 



sent in the water. The same writer 

 gives some observations reported by 

 Dr. Wallich, and apparently consider- 

 ed by Dr. Wallich as very curious, in 

 the Journal of November, p. 206. 

 The phenomena reported by both the 

 above-named gentlemen have repeat- 

 edly came under my notice, as well 

 as the growth of the silicious fila- 

 ments referred to by Mr. Mills in the 

 Journal for January, p. 8; and I 

 have observed a similar growth on 

 frustules of Nitzschia. From my ob- 

 servation.s, I believe these silicious 

 filaments to be mere adventitious ex- 

 crescences, like a wart or tumor on the 

 human body; yet I am satisfied that 

 they affect the motion of the diatom 

 on which they grow, just as a rudder 

 or centre-board affects the motion 

 of a verssel, without any connection 

 with the cause of the motion. In 

 one case I observed a very active 

 Nitzschia having eight or ten of these 

 bristle-like filaments, all on one side, 

 one much longer than the others, and 

 this frustule moved in curved lines, 

 the filaments on the inner side, al- 

 though ordinarily this diatom has a 

 rectilinear course. Presently the long 

 filament became entangled in some 

 rubbish, and for a time the diatom 

 swayed back and forth, as on a pivot, 

 when suddenly the bristle broke short 

 off, close to the valve, and the diatom 

 thus freed moved away to some dis- 

 tance, resuming an almost straight 

 course. Since I first saw these fila- 

 ments on a diatom I have frequently 

 recognized them, and doubt not they 

 are often overlooked in the fresh 

 gatherings and detached in boiling if 

 the gathering is cleaned. By means 

 of such filaments, if very small, a dia- 

 tom might seize and carry along ex- 

 traneous matter with which it came 

 in contact, as it is often seen to do, 

 without the filaments being perceived; 

 but this would not account for the 

 traveling of particles along the dia- 

 tom while it is held fast, as so com- 

 monly happens. 



Many of the phenomena connected 

 with the motion of diatoms seem to 



