500 



A.H. Estabrook 



in different parts; it is nevertheless instructive. The changes 

 in the form and size of Paramecium shown by the curve, are the 

 same as seen under the microscope. The first effect is an imme- 

 diate decrease in the width, and at the same time, a shortening of 

 the organism. Further decrease in length takes place, and then, 

 as death approaches, the Paramecia become thicker and slightly 

 longer. I have designated this form of curve as the death curve, as 

 later work shows that its appearance is always followed by death. 



Adult Paramecia put into a ^^NaCl solution died in one-half to 3 

 hours, none living in this strength longer than 3 hours. The same 

 general effects were observed as in the ^^ NaCl solution, except 

 that, extending over a longer period, they were not so marked. 



Adult Paramecia put into a ^ NaCl solution became thinner 

 for about 20 minutes, then gradually regained their normal size 

 and continued to live normally in that solution. 



In order to see if ^^- NaCl and the more dilute solutions of NaCI 

 had any effect upon size in adult Paramecia which were kept in 

 them for longer periods of time, the following experimen t was tried : 

 One hundred Paramecia taken from the stock culture were put 

 into each of the following solutions, ^, ^^, -^ and -^ NaCl, and 

 a control composed of hay infusion (the same as that used for 

 the solvent in the NaCl solutions). The Paramecia remained 

 in the solutions 48 hours, were then taken out, counted, killed, 

 and measured. This was done several times but as the results 

 were in every case the same, only one series is reported here (see 

 table VII). 



TABLE VII 



Dimensions of Paramecia that have remained 48 hours in various strengths of sodium chloride, compared 

 with controls. Measurements are in microns and each is the average taken from $0 specimens. 100 

 specimens in each watch glass at beginning. 



