G7B GEOFFREY LAP AGE 



at or near the end of the amoeba which was posterior in progres- 

 sion, this was not invariably the case. The sphere might be 

 extruded at the side or at any other point. Probably it is 

 correct to say that, when the amoeba was progressing rapidly 

 in one definite direction, extrusion usually occurred at or near 

 the posterior end ; but when the amo(fba was putting out 

 pseudopodia in all directions and was not changing its position 

 much, extrusion might then occur at any point of its surface. 

 This is probably true of ordinary defaecation also. When the 

 ingested body was about to be extruded it appeared as in Text- 

 fig. A, 13, and was usually, though not always, surrounded 

 by a well-marked vacuole, pinkish in colour, and separated 

 from the water only by a thin layer of protoplasm. This layer 

 became thinner and thinner, until it was reduced to a mere 

 membrane. Finally it was broken at one point. The ingested 

 sphere then seemed to be forced out, slowly at first and then 

 more rapidly, and at the same time the two halves of the 

 enclosing membrane were witlldra^\^l along its sides, so that 

 the opening to the water was widened (Text -fig. a, 14, 15, and 

 16). A final effort of expulsion then quite suddenly forced the 

 ingested body out and the cavity which it had occupied 

 rapidly closed. 



That an active effort of expulsion occurred is suggested by 

 the fact that the ingested sphere did not merely slide out, 

 but was projected by the force of the expulsion well away from 

 the side of the amoeba. This may have been, however, merely 

 the result of the explosion of the fluid vacuole in which it lay. 



The important detail to be noted here is the fact that the 

 vacuole containing the sphere sometimes contained diatoms 

 or the partially digested remains of zoochlorellae, as well as the 

 sphere, and that these were expelled with it and lay with it 

 free in the water. This is a small point which suggests that 

 the sphere had been ingested at the same time as the diatoms, 

 that the vacuole in which it lay was a true food vacuole, and 

 that the sphere was an ingested organism and not a body 

 formed by the amoeba itself. 



