
THE MOTION OF DIATOMS, 177 



musce, and afterwards Saprolegnia ferax. But it has been shown 
more recently, by the work of Cienkowski, De Bary, and Berkeley, 
that this aérial fungus, so common on flies in the autumn, is only 
a terrestrial and imperfectcondition of an Achlya knownas prolifera, 
and which in an early aquatic state is shown slightly magnified in 
Plate IL, Fig. 6. ‘‘ This plant forms resting spores like Vaucheria; 
and there is every probabilty that they are generated by a like 
sexual process. ‘They may remain unchanged for a long time in 
water when no appropriate zzdus exists for them; but will quickly 
germinate if a dead insect or other suitable object is thrown in.” 
The tubes contain a colourless, slightly-granular protoplasm, the 
particles of which are seen to move slowly in streams along the 
walls as in Chara, the currents anastomosing with each other. 
(Zo be continued. ) 

THE MOTION OF DIATOMS. 
By C. M. Vorcr, F.R.M.S. 
T is with great pleasure that I observe the awakening of interest 
in this phenomenon. Like many others, I have watched faith- 
fully the curious movements of the diatoms, in the effort 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 
predicament 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 subject, 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. ‘Therefore, 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, Nitaschia sp., Synedra Sp., 
Surirella turgida, Surirella biserrata, Surirella splendida(?), Cyma- 
topleura solea, C. Hibernica, Cymbella cuspidata, Navicula crypto- 
cephala, NV. cuspidata, Pinnularia viridis ; and apparent movement 
in Stephanodiscus Niagara, in a Gomphonema, and in Cymatopleura 
elliptica. Also I have seen detached valves, free of endochrome, 
exhibiting apparently voluntary motion which, it is obvious, must 

*American Monthly Microscopical Journal, March, 1882. 
