12 FEESH- WATER RHIZOPODS OF NORTH AMERICA. 



the mud in which they had been buried, to occupy a position on its surface, 

 where they receive the full benefit of the conditions necessary to their life. 



From the living' film, as it might not inappropriately be called, the 

 desired objects for examination are to be obtained. Portions ma} r be lifted 

 with a glass tube closed at the upper end by the finger, and then with the 

 other end brought into contact gently with the surface of the ooze. By 

 raising the finger, the pressure of the water forces a portion of the ooze into 

 the tube, when, the finger being replaced, a drop of the contents of the tube 

 may be transferred to a glass slide or an animalcula cage for the field of 

 the microscope. 



The materials collected and disposed of in the manner above described 

 may be preserved in a good condition for examination for weeks together, 

 and indeed without any further care in this way I have kept a stock of 

 Rhizopods alive during the winter. 



The Rhizopods collected with wet Sphagnum, or other mosses, or on 

 damp earth, .may be readily kept in good condition for examination in glass 

 cases, for which purpose common wide-mouthed candy -jars answer. They 

 should be kept in the light in the same manner as the dishes of water. 

 With Sphagnum I have retained its peculiar Rhizopods alive the whole year 

 through. 



To examine the Rhizopods of Sphagnum or other mosses, or from the 

 algous film of damp places, wet a fragment, teaze it with a knife and 

 forceps, and press the water from the pulpy mass into a watch-crystal. A 

 drop of the sediment collected is then to be transferred to the field of the 

 microscope. 



The different forms of fresh- water Rhizopods are not generally restricted 

 to different localities or positions, but are commonly found more or less in 

 association together. Usually the naked forms, and especially the larger 

 ones, the Difiiugias and the Arcellas, are found most frequently, abundantly 

 and best developed, in the ooze of bodies of water. The Euglyphas, 

 Nebelas, and their nearer allies, are in like manner most frequent in the 

 moist Sphagnum of bogs ; and the Heliozoa in the positions previously 

 indicated. 



The chief localities from which I have myself collected the materials 

 of the present work are as follows : 



