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ARABIAN NEMATODES, 



The principle underlying my process of collecting free-living 

 Nematodes is one long practised by prospectors. I prospect for 

 Nematodes in the same way that a miner prospects for gold. 

 Suppose, for instance, that the sand of some beach or fresh-water 

 stream is inhabited, as often happens, by Nematodes and other 

 minute organisms. To quickly isolate these little animals in great 

 numbers the collector has only to profit by the fact, that in standing 

 water sand sinks at once, while small organisms sink rather slowly. 

 Put half a pound of the sand with a pint of water into a dish of 

 the form and size of an ordinaiy one-quart fruit-tin. Having a 

 second beaker or fruit-tin at hand empty, pour the water and sand 

 rapidly back and forth until the water is well roiled — then sud- 

 denly stop. The sand at once sinks to the bottom of the dish, 

 but the organisms remain for a few seconds partially suspended. 

 The instant the sand reaches the bottom of the dish, pour the super- 

 natant fluid containing the organisms into a third dish and there 

 let it stand until clear, when the sediment of organisms may be 

 obtained in a very satisfactory state by decanting the clear water. 



To collect from mud, reverse the pi^ocess ; that is to say, after 

 agitating the mud and water allow the roily mixture to stand 

 until the organisms have settled, then pour away the muddy 

 water. Eepeat this process until the desired result is obtained. 



In collecting from algse it will be found best to use a large 

 shallow dish. Place the algse in the dish with an abundance of 

 water. To separate the Nematodes from the algse, stir the latter 

 briskly about in the water, squeezing them often, and finally 

 wring them dry and throw them away. Allow the washings to 

 stand for a quarter of an hour, and then decant. Put the sediment 

 into deep dishes, and treat as directed for sand or mud, or both, 

 as may be necessary. 



To collect from culms of grasses or sedges or from other land 

 plants, cut a quantity of the plants and put them into a wash-tub 

 and cover them with water. Allow them to soak an hour, then 

 proceed as wnth algse. 



