52 Journal of the Mitchell Society [August 



Average Kate of 

 % of Agar No. of Amoebae Used m 4. j.- 



* Contraction 



2.5 19 43.8 



The table shows a discrepancy in the rate of contraction of the 

 vacuoles in amoebae grown on 1.0 per cent agar. This is due to the 

 condition of the amoebae which were studied. The culture was not in 

 a flourishing condition so that only a few amoebae could be obtained 

 and the rate of contraction of their vacuoles was much slower than 

 the rate in any of the other amoebae studied. In other respects there 

 is a gradual increase in the rate of contraction of the vacuoles when 

 the amoebae grown on 0.5 per cent agar are compared with those 

 grown on 2.5 per cent agar. 



This increase in the rate of contraction of the vacuoles when 

 amoebae are on a denser medium may be due to an attempt on their 

 part to reach that special relationship between the consistency of the 

 medium and the consistency of the cell plasm which has been shown 

 to exist for amoebae (Hogue 5). 



While performing the previous experiments it became evident that 

 the age of the amoeba had some effect on the rate of contraction of the 

 vacuole. Here by age of the amoeba is meant not the age of one par- 

 ticular amoeba but the age of the whole cycle of growth on the Petri 

 dish. Accordingly a series of experiments Avere performed to deter- 

 mine the relation between the age of the amoeba and the rate of the 

 contraction of its vacuole. Media made up with 1.0 and 1.5 per cent 

 agar were used in the different series of experiments, as these had 

 proved the best densities for the cultivation and study of amoebae 

 (Hogue 5). Two different kinds of Limax amoebae, A P^ and A W, 

 were used and the results compared. 



