A Strange Place for Rotifers. 211 



A STRANGE PLACE FOE ROTIFERS. 



BY HENKY J. SLACK,, F.G.S., 

 One of the Hon. Sees, of the Microscopical Society of London. 



In the writer's garden hangs a Mason's hygrometer, or wet 

 and dry bulb thermometer. The supply of water to keep the 

 wet bulb moist is held in a small glass vessel about one inch in 

 diameter, and rather more than that in height, and having a short 

 neck, just wide enough to allow some threads of lamp cotton 

 to hang freely through it. It may therefore be described as a 

 small glass, squat bottle, loosely stoppered with lamp cotton. 

 Every two or three days in warm dry weather, and every two 

 or three weeks in wet weather, this vessel requires replenishing, 

 which is usually done by holding it under a tap, and suffering 

 the stream not only to fill, but to give a good washing to the 

 cotton and to the vessel. When the cotton is dirty it is re- 

 moved, and fresh supplied. No green matter of any kind has 

 grown in the vessel, and very little atmospheric dust could 

 find access to it. Under these circumstances it could not be 

 expected to be a favourable place for any kind of infusoria, 

 but in August the cotton fibres became slimy without getting 

 discoloured, and this circumstance led to a microscopic exami- 

 nation. There was no decay in the cotton fibres, and very 

 little extraneous matter adhering to them, but the slimy matter 

 resulted from the presence of a considerable number of infu- 

 soria, among which were many rotifers of small size and of the 

 common sort. 



The chief infusoria in point of numbers were monads of 

 minute dimensions, some swimming freely with a jerking mo- 

 tion, and others jumping violently without much change of 

 place. With the help of Smith and Beck's one-twentieth 

 and first eyepiece, giving a magnification of 1000 linear, it 

 was seen that these little objects were provided with single 

 tails or filaments, and were able to adhere to the glass by the 

 extremities of these organs, and being thus moored fast to a 

 fixed point, they executed a series of jerking jumps in all 

 directions, with great liveliness. The body of these little 

 monads was white and pear-shaped, about 1 — 8000" in greatest 

 diameter, and more or less filled with smaller cells. The tails 

 or filaments were exceedingly fine, and four or five times the 

 length of the bodies. A few small ciliated infusoria were also 

 present. The rotifers were numerous and very lively, though 

 apparently stunted in growth by the limited supply of food. 



Part of the cotton was transferred to a Preston salts bottle 

 filled with cistern water, and left uncovered, so as to catch 



