CANNIBALISM IN AMOEBA 673 



amoebae with only one contractile vacuole were at least as 

 common. 



Doflein (9) placed some of his amoebae in a cultm-e which 

 contained Prontonia leucas which were full of green 

 zoochlorellae. The amoebae fed upon the ' remains ' of the 

 Frontonias and themselves became infected with zoochlorellae. 

 A similar infection occurred in come of my cultures also, the 

 zoochlorellae being acquired in this case apparently from Par a- 

 moecium bur sari a. These zoochlorella-inf ected amoebae 

 were not, however, used for any of the observations described 

 below and there is no evidence that cannibahsm occurred in them. 



The cultures also contained other small amoebae, which 

 were definitely different in external appearance from the 

 Amoeba vespertilio, and which remained so. As far as 

 I was able to judge from external characters only, these small 

 amoebae were of the Amoeba limax or Vahlkampfia 

 type. Their average size was 28-30 A' long by 6-8 fJ- broad ; 

 but their length varied from 20-50 n, and their breadth from 

 4-12 fi. They possessed a vesicular nucleus, similar in structure 

 to that of Amoeba vespertilio, its diameter being 

 5-6 fi, while the diameter of its endosome was 3 yw. These 

 amoebae were present in large numbers in some of the cultures, 

 especially in the later stages of the work. 



A few amoebae, with a diaphanous appearance, rather larger 

 than the A. limax and without the slug-hke form which is 

 characteristic of the latter, were not identified. They may have 

 been either large A. limax forms or small examples of 

 Amoeba vespertilio, or they may have belonged to 

 another species altogether. 



Other Protozoa present in the cultures included Para- 

 moecium bursaria, Pleuronema chrysalis, and 

 numbers of small Flagellata. No Thecamoebida were ever seen. 



3. Observations on the Spheres. 

 The amoebae had not been long under observation before 

 attention was arrested by certain remarkable inclusions which 

 many of them contained. 



