PRESIDENT S ADDRESS. XXI 



vaiy greatly in size, and while some are more than one-tenth of 

 an inch in diameter, others appear as mere specks even with an 

 amplification of four or five hundred diameters, so that it is only 

 the larger forms which may be picked out in the way described. 



Then at first they seem particularly difficult to handle and 

 isolate, being usually found so near the mud, or mixed with it ; 

 but a little study of the habits of these organisms shows a 

 ready way to get over that difficulty. 



Not being swimmers, though doubtless like the hydra they 

 possess the power to rise or fall in the water, and have besides 

 some slight means of free locomotion, they are usually found to 

 attach themselves to anything with which they may come in 

 contact, generally decayed weeds or mud, and it is only necessary 

 to take advantage of this habit to obtain them quite free from 

 everything else. 



Take up some mud and water in which they are plentiful 

 and fill a thin trough ; lay it nearly or quite flat upon the stage 

 of the microscope and allow it to remain there a few moments ; 

 then quietly empty out the mud and dirty water at one end 

 while you replace it with clean at the other, and the Amoebae 

 will be found attached to the glass as clear as the noonday sun. 

 Care only needs to be taken that the clean water shall replace 

 the dii'ty without exposing the animals to the air or they will 

 fall to pieces in countless granules, an experiment worth 

 noting. 



It requires but a little practice even to pick out of a trough, 

 while under the one inch, any particular specimen, and place it 

 by itself on a slip of glass or compressor, provided a very fine 

 tube di-awn out to the thinness of a hair at one end, and having 

 an india-rubber teat with the aperture sealed at the other, is 

 used for the purpose. 



Here, again, black back-ground illumination, with a suitable 

 power and binocular instrument, will demonstrate that the 

 Amoeba is not the bit of flat protoplasm it is usually supposed 

 to be, but a creature having both breadth and depth, able to 

 attach itself to the top glass by some of its pseudopodia while 



