CANNIBALISM 'iN AMOEBA 691 



tained it. At any rate no damage was demonstrable, and the 

 amoebae lived and multiplied normall}' while they contained 

 spheres, and are, indeed, still living at the present time in 

 the same cultures, although only rarely do they now contain 

 spheres. 



Secondly, if the spheres were parasites it is difficult to imder- 

 stand why they were so frequently extruded by the amoebae. 

 When a parasite has gained entrance to its host it usually does 

 not leave it, except for the purpose either of propagative repro- 

 duction or of mechanical distribution of its species. Such 

 a parasite would, at some time or other during its sojourn in 

 its host, be likely to show some evidence of its reproductive 

 cycle. The spheres, however, never showed any signs of any 

 reproductive capacity whatever, either when inside or outside 

 'the amoebae. They were taken in and passed out in the same 

 manner as ordinary food matter would be ingested and extruded, 

 behaving in a strictly passive manner. 



It occurred to me that the amoebae and the spheres might be 

 symbionts or commensals. Against this highly improbable 

 theory was the fact that a vacuole, filled with fluid, was present 

 round the sphere. In other cases of symbiosis among the 

 Protozoa, as, for example, that of the zooxanthellae and 

 zoochlorellae, the latter occurring under certain conditions in 

 the very amoebae under consideration, no vacuole surrounds 

 the algae. 



(2) The Hypothesis of Endogenous Budding. 



The second hypothesis, that the spheres were endogenous 

 buds, was much more attractive and led me astray for some time. 

 I should have hked to have been able to prove that they were 

 buds, and very nearly succeeded in convincing myself that they 

 were. But the finding of such structures as those shown in 

 PI. 28, figs. 1 and 2, and PI. 29, fig. 7, where two, three, or four 

 amoebae were enclosed within one another, seemed to stretch 

 the theory of endogenous budding rather far. Before ascribing 

 such remarkable structures as these to endogenous budding it 



