20 ACTION OF AUXETICS AND KINETICS 



excystation will not take place unless there is a 

 constant slow stream of fluid beneath it. For 

 example, if the muslin is made to dip into the 

 solution all round, no excystation occurs, since 

 there is a condition of stagnation, and a deficiency 

 of bacterial growth under the cover slip ; whereas 

 cysts placed on the slide external to the cover- 

 glass excyst in about twenty-four to forty-eight 

 hours (PL I., B). If the circulation beneath the 

 cover-slip is made more rapid by tilting the slide, 

 no excystation again takes place, as the products of 

 bacterial action which effect this are washed away. 

 A thin film of jelly can be spread on the glass 

 slide, and this in its turn covered with the muslin, 

 and, by this method, excystation can be observed 

 on a jelly surface. 



Method A, 2. The principle of the above method 

 was adopted and an improvement made by using 

 thicker cloth (calico) which had a circular hole 

 cut in the centre slightly larger than the diameter 

 of the cover-slip the latter being prevented from 

 pressing on the amcebse by interposition of strips 

 of paper. This apparatus has been very useful for 

 the prolonged examination of amcebag exposed to 

 the action of auxetics and kinetics, as it enables 

 continuous observations to be carried out in- 

 definitely with very little trouble, and is more 

 satisfactory than many of those which have been 

 employed. A short description of such a " live 

 slide " may be given here : 



Live Slide (PL II., A and B). A plate of thin 

 glass about three inches long and two inches wide 

 has a narrow glass arm cemented to it along the 

 short end, forming a projection upon which a small 



