Rotifers 



FLUID WHOLEMOUNTS AQUEOUS TYPE 



29 



ring when mounting is critical; it must 

 have dried to a rubbery, but not to a hard, 

 consistency. For the final mounting one 

 requires at hand the shdes which have 

 been prepared, the turntable which was 

 used to draw the original ring, some clean 

 covershps, a pipet of the eye-dropper type, 

 and the concentrate of algae. 



A slide is centered on the turntable and 

 a twist given to the turntable to make 

 sure that the centering is accurate. A drop 

 of the concentrated algae is placed in the 

 center. If the slide is clean this drop will 

 flow outwards until it reaches the cement 

 ring where it will be held. Under no cir- 

 cumstances may the coverslip be placed 

 on the preparation until the fluid touches 

 the ring at all points. If it does not do so 

 at once it may be brushed out with a small 

 brush. It does not matter in the least if it 

 flows over the ring but it will be impossible 

 to avoid including air bubbles if it does 

 not reach the ring. A coverslip, held 

 between the thumb and the index finger 

 of the right hand, is lowered horizontally 

 until it touches the drop of algal suspen- 

 sion. It is then dropped in such a manner 

 that it falls onto the ring which should be 

 centered exactly under the coverslip. If 

 it is not centered it is still possible to ad- 

 just it with a needle, provided it is not too 

 far out, as long as it has been dropped and 

 not pressed down. If it is initially pressed 

 down, so as to make a contact with the 

 gold size, nothing can be done and another 

 sUde must be taken in its place. As soon 

 as the coverslip is centered a fine needle 

 is taken and run round immediately over 

 the ring to press the glass into contact 

 with the slightly tacky gold size. Any 

 of the algal suspension which has crept 

 onto the top surface of the coverslip is re- 

 moved with a soft cloth, remembering 



to be very careful not to shift the cover- 

 shp; any fluid which has spread out over 

 the shde may he wiped off as far as the 

 edge of the coverslip itself. There will still 

 remain a small quantity of the fluid be- 

 tween the ring, which is slightly smaller 

 than the coverslip, and the edge of the 

 coverslip itself. This must be removed, 

 using the edge of a sheet of filter paper 

 which is touched down to the fluid. 



The withdrawal of this superfluous 

 fluid from between the edge of the cover- 

 shp and the ring, is a critical part of the 

 proceedings. The ring on which the cover- 

 slip rests is not sufficient to prevent 

 evaporation but is sufficient to prevent 

 the introduction of air mechanically while 

 this superfluous fluid is being withdrawn. 

 If, however, the coverslip is ever so 

 shghtly raised by the edge of the filter 

 paper an air bubble will inevitably enter 

 the mount which must then be thrown 

 away. Assuming that all has gone well, 

 and that the superfluous fluid has been with- 

 drawn, a heavy ring of gold size is turned 

 on and the mount placed on one side. 

 The ring of gold size should be at least }i 

 of an inch wide and as thick as the ma- 

 terial can be persuaded to flow from the 

 brush. The mount is then placed on one 

 side and the next one taken. 



A single ring of gold size will hold the 

 mount in good condition for a few months 

 but if permanence is desired it is better to 

 add three other rings of gold size at daily 

 intervals, then to wait a week and to turn 

 on top of this a coat of asphalt varnish. 

 The degree of permanence of these 

 mounts is variable. The writer has one in 

 his possession which is more than 20 

 years old and is as good as it was the day 

 it was made. 



Preparation of a Wholemount of a Rotifer by the Method of Hanley 1949 



The method of Hanlev is a modification narcotic (Chapter 19, AF 50 Rousselet 



of the well-known method published by 1895), and the sjiibstitution of formalde- 



Rousselet 1895 (11479, 5:1) which has hyde for osniic^'acid in kiUing. These 



been quoted without alteration in the substitutions not only render the final 



literature for more than 50 years. Han- preparation better and more permanent 



ley's method involves narcotization in his l)ut also remove the difficulties both of 



own narcotic (Chapter 19, AF 50 Hanley working with osmic acid and of securing 



1949) as a substitute for Rousselet's cocaine. This method is of great impor- 



