318 THE FOEAMINIFEEA 



needle or stiff brush ; vertically if one wants a trans- 

 verse, or horizontally if one wants a vertical, section. 



' At this point it is necessary to be sure whether 

 the balsam is of the right consistency, i.e. neither 

 too hard nor too soft ; in the former case it will 

 splinter away and the test be torn from its position, 

 and in the latter the rubbing action of the stone will 

 crush the walls of the chambers. If, however, you 

 always use the same balsam and the same method of 

 heating it, you will soon be able to bring it always 

 to the required condition, but to make sure it is 

 advisable to take up a tiny drop of the balsam whilst 

 still soft with a needle and let it cool, and if it 

 crumbles into fragments when pressed upon the 

 finger-nail you can safely proceed with the operation. 



' Place the cover slip upon a flat surface, place a 

 moistened plane of the grinding-stone (or hone) 

 upon the test, and commence rubbing it softly with 

 a circular movement of the hone. The greatest 

 care must be taken to keep the hone absolutely 

 parallel to the plane of the section you desire to 

 make, as the test wears down and the hone rubs 

 closer to the cover slip. One cannot see the pro- 

 gress of the operation with the naked eye, but the 

 section in progress must be constantly examined 

 under the microscope, washing away the muddy 

 detritus of the test with a wet brush before each 

 examination. Almost immediately the internal 

 chambers make their appearance, outlined in white 

 on the yellowish matrix formed by the balsam, and 

 one continues until one judges that one is almost 



