COLLECTION OF BDELLOID AND OTHER ROTIFERA. 213 



of the nets an inch or two above the surface. The water- weeds 

 are then stirred and shaken about and washed in the net as in 

 a bucket in order to detach the organisms which adhere to them. 

 The plants are then thrown away and the coarse net lifted out- 

 of the fine one and allowed to drip into it. We then have in 

 the fine net only microscopic organisms and fine sediment. It 

 has been found by experience that even very large Kotifers 

 will readily pass through the No. 6 net. Possibly giants like 

 Stephanoceros would not pass through, but such animals are 

 found by the direct examination of portions of water-plants 

 under the microscope." 



Where the broad leaves of water-lilies, or even the floating 

 leaves of Potamogeton occur, it is worth while to gently scrape 

 the under surfaces, placing the result in a separate receptacle 

 for home examination. It is also worth while to occasionally 

 examine the egg-masses of w^ater-snails, when these are available 

 either in freshly collected weed or on the sides of aquaria. 



In ponds, ditches, canals, rivers, etc., there is sometimes a 

 stone-faced bank or other stone- or woodwork in the water. 

 When it is possible I make it a rule to put my hand below the 

 surface to feel if there be a submerged growth of any kind upon 

 the accessible portions. Sometimes one finds short-stemmed 

 mosses, sometimes a thick furring of thread-like algae, some- 

 times only a slimy coating. Any of these are worth taking home 

 for examination. One can either pick off a little with the finger 

 and thumb or use a flat-sided tobacco tin to scrape off a square 

 inch or two. Several species of the Bdelloida (for instance, the 

 elusive Philodina erythrophthalma) are best got by this method, 

 which for a long time I thought had not been employed by 

 earlier w^orkers. Recently, however, I read in Eichhorn's in- 

 teresting book that he was accustomed to collect such material 

 about a hundred and forty years ago. 



In some places it is possible to scrape from the upper portions 

 of partially submerged stone a dried encrustation of algae, which 

 had been submerged when the water was at a higher level. 

 Samples of such crusts should be taken, and treated as will be 

 presently described for dry mosses. 



One more method of pond work should be kept in mind. It 



