CANNIBALISM IN AMOEBA 687 



referred to, which was kept under observation, the sphere 

 returned to the spherical form after it had been inside the 

 amoeba about five hours. Later it became less and less distinct, 

 and seven hours after it had been ingested it could no longer 

 be distinguished. Apparently it had been digested. This was 

 the only instance in which anything like digestion of the 

 spheres was seen. In all other cases which were kept under 

 observation the spheres were sooner or later extruded by the 

 amoebae which had digested them. 



One other point remains to be mentioned before we discuss 

 the nature of the spheres. It is illustrated by PI. 28, figs. 1, 2, 

 and 4, and PI. 29, fig. 7, drawn from stained preparations, in 

 which several examples of it were found at different dates. 

 PI. 28, figs. 1 and 2, show the phenomenon in its most typical 

 form, and it will be seen, on reference to them, that there 

 are here as many as four amoebae, enclosing one another, 

 giving the impression of concentric fission. The figure looks, 

 at first sight, like the dream of a pre-formationist, but we shall 

 see that it has a much more prosaic explanation. It is so 

 remarkable that I at first believed it to be an artefact, due, 

 I supposed, to drying of the preparation, or to imperfect fixation. 

 The other organisms on the slide were, however, well fixed and 

 stained, and these remarkable structures did not occur on 

 slides of one batch only but were present on slides made on 

 widely different dates. Further, I saw^ what I interpreted as 

 the same structures in the living organisms, although I was never 

 able to convince myself of this. In any case the phenomenon 

 admits, as we shall see, of a perfectly natural explanation if 

 we adopt the only hypothesis which fits the whole of the facts. 



There can be no doubt that there are actually several 

 independent amoebae enclosing one another, because their 

 nuclei are perfectly distinct and each amoeba possesses a vacuole 

 for the reception of the others. The nuclei are, moreover, all 

 exactly similar in structure to one another. PI. 29, fig. 7, is 

 perhaps the most remarkable and was the most difficult to 

 interpret. There are here present seven nuclei, and the inter- 

 pretation of the figure is best deferred to a later stage (cf. 

 below, p. 700). 



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