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Note on Some Minute Forms of Pond Life. 

 By Edward M. Nelson, F.R.M.S. 



(Read January 19th, lS9ij 



In pond-life observations, conducted under low and mediiiin 

 powers, especially when a dark ground is used, minute organisms 

 may often be seen sparkling like dust. The examination of 

 these dust-like bodies under a high power has revealed, among 

 a host of ordinary and common bacilli, not a few strange 

 forms, an account of which will perhaps be of interest. 



First let me state that in this kind of observation, when 

 using an oil immersion ^^2 ^^^ powers of 1,500 diameters, I 

 found Rousselet's compressor invaluable ; with it work was per- 

 formed as easily as on an ordinary balsam-mounted diatom. 



I will first describe three filamentous bodies, which, though 

 somewhat of the same shape^ were evidently quite distinct, and 

 functionally different from one another. 



1. An organism having a thread-shaped body, varying in 

 length from, say, a half-thousandth to one-thousandth of an 

 inch ; excessively thin, say yoO"oir ^^ 8"oS"oo ^^^^ 5 ^^ structure 

 visible ; movement, a stiffish bending. A bacterium in a lep- 

 tothrix stage (?) 



2. Was also a rod-shaped body, longer and a little thicker 

 than the former. Numerous granules could be detected inside 

 when the aperture of the condenser was fully opened and the 

 resolving power of the objective pushed to its utmost capa- 

 bilities. The movement was backwards and forwards like a 

 Melosira. A diatom (?). 



3. "Was a similar shaped organism, about one-thousandth of 

 an inch long, having an elliptical swelling in the middle. This 

 elliptical portion was about ^^ of the whole length of the 

 organism. No structure could be detected. Its movement 

 was not at all amoeboid, but more like that of a worm. The 

 largest of these three organisms was not so thick as a common 

 spirillum. 



