Dr. Wallicli on the Amoebae. 219 



admirably described and christened Amoeba viUosa, and all 

 its oddities are explained ; there the reciprocal nature of the 

 endosarc and diaphane " (a name given to the ectosarc hy 

 Carter) , " the nature of the nucleus, and the method of its 

 subdivision, and, indeed, the exact morphology of the Amoeb(B, 

 is given to perfection. . . . One thing has struck me, and 

 that is that there are two species of Amoeba only, and not a 

 score. There is A. villosa, which is a really crowned head ; 

 then there is the other, which, according to locality, time, 

 season, food, and the eyes of the observer, changes its general 

 shape and receives many names, and is called A moeba princeps. 

 It ought to be -4. communis, as it is plebeian to the regal 

 villosay—Pop. Set. Rev. 1877, p. 217. 



De. Gruber (" Contributions to the Knowledge of the 

 Amoebce^^). — " Auerbach, as is well known, starting from the 

 assumption that a membranous boundary was a necessary 

 attribute of a cell, set up a theory, quite compatible under the 

 circumstances of the time, according to which the Amoebce 

 also, as unicellular creatures, had a membranous envelope. 

 This opinion was refuted by subsequent naturalists, and it 

 was Greeff principally who gave a more correct interpretation of 

 Auerbach's observation." — Translated version of Dr. Gruber's 

 paper, Ann. (& Mag. Nat. Hist. Feb. 1882, p. 106. 



" The melting of the fine cortical layer into the broad clear 

 border does not take place with equal rapidity at all points, so 

 that a part of the Amoeba often appears sharply limited, whilst 

 another is already surrounded by a clear space. ... In this 

 way Amoeba dvffluens can continuously change its aspect 

 completely in one or other of the modes described. Upon what 

 law this power depends cannot be stated definitely j very 

 probably, however, different conditions of pressure come into 

 play in the matter. With a centripetal force acting uniformly 

 upon the whole periphery, the more fluid parts of the proto- 

 plasm are all pressed into the interior, and only the narrow 

 membranaceous boundary remains. This acquires a firmer 

 consistence by contact with water , and therefore at the points 

 where the pseudopodia issue it is pushed a-side by the latter. 

 If the general pressure ceases, the more fluid constituents 

 again come forth from the interior, dissolve the solidified cor- 

 tical layer J and form the clear border. The best illustration 

 of the process is furnished by those cases in which a slow 

 flowing forward of the Amoeba in one direction is taking 

 place. On the advancing side the fluid constituents are pushed 

 on in front ; here all pressure has ceased, whilst it acts on the 

 opposite side, where, accordingly, the cortical contours are quite 

 distinctly to be seen.'''' — Ami. & Mag. Nat. Hist. Feb. 1882 

 pp. 112-113. ' 



