FURTHER NOTES ON DIATOM LOCOMOTION. 



BY T. CHALKLEY PALMER. 



In a former communication * concerning Navicula socialis 

 I mentioned the ability of that diatom to crawl upon vertical 

 surfaces and even to cling to and move upon the under aide of 

 a cover glass. It has also been implied that other species of 

 diatoms may move in this position. I propose here to note 

 some of the rather curious and unexpected circumstances 

 observed in this connection, believing that any data of this 

 sort cannot be quite valueless so long as authoritative writers 

 continue to say that the motion of diatoms is not yet under- 

 stood. 



Anyone who is in the habit of collecting and retaining 

 bottles of water containing diatoms will soon have occasion 

 to note that the motile forms crawl up the sides of the bottles, 

 especially on that side which is best lighted. Within a day's 

 time the walls of the bottle will often be colored a dark 

 amber, and by careful management one may get enough of 

 the deposit under the microscope to show its composition. 

 Most of the naviculoid forms, and many others, will so 

 expand upon the vertical surface against the influence of 

 gravity. Having pondered upon this phenomenon, I thought 

 to give a more difficult task to these diatoms. A fresh gath- 

 ering of Naviaila Iridis was put into a conical Erlennieyer 

 flask and washed carefully into a thin layer on the flat 

 bottom. The flask was then covered completely with black 

 paper and capped with a thimble of tinfoil. A little window 

 was cut in the black paper, about two inches above the 

 bottom, and almost on a level with the top of the water. 

 The flask was then left undisturbed for ten days, exposed to 

 the diffused daylight from a northwest window. At the end 

 of this time the paper was carefully removed, and a scjuare 

 patch, of a dark amber color, was found upon the wall of the 



•Procrkdinos, Vol. VI, p. IlH. 



