ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 251 



Only for a little while, however, did it move ; in a few moments it lost its 

 animation, seemed to become transparent, and at last faded into one of those 

 discs which seem to be merely the shells of once active forms. I did not 

 see it move again. 



This observation was carried on continuously during two hours and a 

 half, and every stage watched most closely. I vfas at a loss what to call it, 

 if not a clear case of conjugation and separation. 



The most convincing proof to my mind that this was a proceeding which 

 was for a purpose, was given when, two nights after, this slide, which was 

 laid carefully aside for future examination, was found to be full of young 

 Amoebse. They literally swarmed ; I counted in the field at one time 

 twenty-four of uniform size, while I have no hesitation in saying that there 

 were between one and two hundred in the slide, which had before held but 

 two. The worn-out disc was recognized, and also what seemed to be the 

 remains of the larger Amoeba." 



Dig^estive Process in some Rhizopods.* — After a brief summary of the 

 observations of previous writers. Miss M. Greenwood describes her own 

 results, which were derived from experiments on AdinosjpJiserium and on 

 Amoeba. 



The act of ingestion. — In Amoeba proteus, in which there is a more or 

 less definite posterior extremity, it is this region that ingests most actively. 

 The food is enclosed by the flowing out of two pseudopodia, which gradually 

 close behind the prey. In the case of quiescent solid matter, very little 

 fluid is included, but when the prey is active, more or less fluid is involved 

 in a vacuole ; but the amount depends on the activity of the prey to some 

 extent. Ingestion was never observed in the anterior, moving region of the 

 Amoeba. 



In ActinospJiserium, the prey can be taken in anywhere ; being captured 

 by two pseudopodia, and enveloped in a film of hyaline protoplasm which 

 advances from the side ; very little water is included. The time taken in 

 the process varies ; sometimes the prey will swim away, after being in 

 contact with the captor for an hour. 



Changes undergone by ingested bodies. — The substances ingested are 

 divided into four groups : (1) Starch, &c. ; (2) Fat-globules ; (3) Proteids 

 (a) enclosed in a resisting wall or (6) " unshielded " ; and (4) useless 

 material, e. g. litmus. In Amoeba the starch was extruded, after some 

 hours or days, unaltered. Fat was likewise unaltered. Protococcus and 

 Torulse were observed as examples of protected proteids ; the torulae were 

 unaltered, except for the loss of vacuoles ; but in the case of chlorophyll- 

 containing bodies, their green colotir was changed to brown, after a day or 

 two, indicative of some action on the proteid. Of " unshielded " proteids, 

 Monas Dallingeri was noticed ; the protoplasm became " turbid " after seven 

 minutes; the flagellum broke down after fifteen minutes. The ingestive 

 vacuole becomes digestive ; but after the first changes on the food, it 

 gradually disappears, and the resulting granules distributed about the 

 Amoeba. In the case of Algse, though the change from green to brown 

 indicates a change in the protoplasm, the cell-wall is not perforated ; this 

 therefore precludes the idea of " direct protoplasmic action," and indicates 

 that the fluid in the vacuole diffuses through the cell-wall. Probably fresh 

 fluid passes into the vacuole, and this then forms a vacuole of ejection ; the 

 act of ejection takes place with some force. But in the case of " unshielded 

 protoplasm " no vacuole of ejection is formed. In Actinosphserium the starch 

 grain was unaltered ; the fat-globtiles appear to be acted on in some way, 



• Journ. of Physiol., vii. (1886) pp. 253-73. 



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