THE SIMPLE TISSUES. 



(//) The gills consist of bars with clubbed free ends, along 

 their edges recognise the movements due to ciliary action. (U) 

 On the edges of the bars the cilia are seen in full face curving 

 towards or away from the observer, whilst at the free unbroken 



FIG. 12. 



ends they are seen in side view. Note the direction of the 

 movement and the manner in which the cilia bend. The cur- 

 rents produced are indicated by the movements of the floating 

 particles in the fluid. Detached pieces of gill occur rotating 

 under the influence of their cilia. 



Effect of chloroform or ether. Raise the cover, introduce a small drop 

 of the reagent into the cell, and replace the cover. 



Watch the gradual slowing and ultimate arrest of the move- 

 ment. As the movement slows observe the way in which the 

 individual cilium bends, it curves from the tip downwards and 

 the extension takes place in the converse direction. If the 

 action of the reagent has not been excessive motion can be 

 restored by removal of the reagent. 



Free the cell of its gaseous contents, lift off the cover, remove the 

 paper cell with forceps, and after rinsing the latter in water replace 

 them in position. 



The cilary action will slowly return. This is an instance 

 of the action of an anaesthetic upon living protoplasm. 



Effect of heating-. Using the same preparation and omitting the 

 paper cell, place it on the hot stage upon the stage of the microscope. Turn 

 the end of the tin plate which projects beyond the stage slightly upwards 



