CANNIBALISM IN AMOEBA 693 



is present while the bud is still within the parent. It is, in fact, 

 one of the first of the organellae to appear, and its presence can 

 be taken as an indication that bud formation is in progress 

 (Lapage and Wadsworth, 17). In the spheres, on the con- 

 trary, a contractile vacuole was never seen while the sphere 

 was within the amoeba. It did not appear in the sphere until 

 an appreciable interval had elapsed after the sphere had been 

 expelled. 



Further than this, endogenous buds, in other groups of 

 Protozoa, do not usually vary much in size in any particular 

 species producing them. They are cut out of the parent to 

 a definite size which remains unaltered, and it is not true that 

 they are smaller when they are first formed and that they grow 

 to a mature size before their birth. The spheres, however, 

 although they show a striking uniformity of structure, do vary 

 a good deal in size, some being as small as 10 fJ- in diameter, 

 others up to 46 /^. This variation in size suggests that they 

 are not endogenous buds. Further, in the smallest ones the 

 nucleus is fully formed and typical, measuring 6 /^ in diameter, 

 the endosome measuring 3 /x in diameter. This is a significant 

 fact, when we remember that the nucleus of the A. limax 

 also present in the culture is 5-6 /J- in diameter with an endosome 

 of 3 /x. The variation in size of the spheres is, therefore, more 

 simply explained on the hypothesis that they represent amoe- 

 bae of different sizes which have been ingested, than in any 

 other way. 



The fact that some of the spheres developed, after they were 

 extruded, into typical small amoebae certainly suggested that 

 they were reproductive bodies ; but this was just as easily 

 explained as the escape of an ingested amoeba after successful 

 resistance to the digestive juices of its captor, and such an 

 explanation was more in accordance with the other facts. 



Another important fact against the view that the spheres 

 were endogenous ])uds was the observation that the spheres, 

 while inside the amoebae, often contained diatoms and other 

 food matter in food vacuoles (PL 28, figs. 2 and 5, and PI. 29, 

 figs. 7, 8, and 9). This is highly significant in view of the fact 



