27 



LESSON VIII. 



:.' STUDY OF CILIA IN ACTION. 



1. MOUNT in sea-water one or two bars of the gill of the marine mussel 

 (fig. 27). Study the action of the large cilia. Now place the preparation 

 upon the copper warm stage (see Lesson V.) and observe the effect of raising 

 the temperature. 



FIG. 27. VALVE OF MUSSEL (MYTILUS EDULIS) SHOWING br, br, THE EXPANDED 



GILLS OR BRANCHIAE, WHICH, OWING TO THE LITTLE BARS OF WHICH THEY 

 ARE COMPOSED, PRESENT A STRIATED ASPECT. 



ml, mantle ; m, cut adductor muscle ; i, mass of viscera ; the dark projection just above is the foot. 



Keep this preparation until the end of the lesson, by which time many of 

 the cilia will have become languid. When this is the case pass a drop of 

 dilute potash solution (1 part KHO to 1,000 of sea-water) under the cover-glass 

 and observe the effect. 



2. Cement with sealing-wax a piece of small glass tubing to a slide so that 



FIG. 28. MOIST CHAMBER ADAPTED FOR PASSING A GAS OR VAPOUR TO A 

 PREPARATION UNDER THE MICROSCOPE. 



one end of the tube comes nearly to the centre of the slide. On this put a 

 ring of putty or modelling wax half an inch in diameter so as to include the 



