10 FRESH-WATER RHIZOPODS OF NORTH AMERICA. 



pected and occasionally a surprisingly rich supply of Rhizopods, and 

 repeatedly the most promising places have yielded exceedingly few. 



The Rhizopods may be found at all temperate seasons of the year; 

 and even in winter, when out of the influence of a freezing cold, a few 

 may be discovered, though mostly in a comparatively inactive state. Frost 

 or a freezing- temperature appears to destroy them. 



They do not live among actively decaying vegetal matter, nor are 

 they to be found in foul water. I have further not been able to discover 

 them in brackish waters on the sea-coast, though I detected a few forms in 

 feebly saline or alkaline waters in the Bridger Valley of Wyoming Territory. 



The Fresh-water Rhizopods appear to inhabit indiscriminately almost 

 any kind of country, no matter what may be its rocky constitution, except 

 it be limestone. According to my experience, they are comparatively 

 rare in limestone districts, and I have repeatedly been disappointed in 

 my expectation of finding them in some large limestone springs in which 

 grew a profusion of Anacharis, Chara, and other aquatic plants. This has 

 appeared the more surprising when it is considered that the allied marine 

 order, the Foraminifera, have so largely contributed to the formation of the 

 limestone rocks. 



The mode I have habitually adopted for collecting Rhizopods, which 

 is also equally well adapted for collecting man} other microscopic organ- 

 isms, plants, and animals, is as follows : 



For ponds, ditches, or other waters, I use a small tin ladle, or dipper, 

 such as is commonly employed for domestic purposes Into the handle I 

 insert a stick of convenient length, and for this I usually carry with me 

 a jointed pole of two or three pieces, each about five feet. The dipper 

 is used by slowly skimming the edge along the bottom of the water so as 

 to take up only the most superficial portion of the ooze, which is then 

 gently raised from the water and transferred to a glass jar. A small hole 

 in the bottom of the ladle favors the retention of the collected material, 

 but care should be taken that it is not so large as to permit the material 

 to stream through. After the collecting-jar is full, if more of the material 

 is wanted, after allowing that in the bottle to settle, I pour off a portion 

 of the water and supply an additional quantity from the locality. 



Usually, I have proved more successful in obtaining Rhizopods from 

 the ooze near the shores of lakes and ponds than I have in deeper water; 



