110 Dr. A. Gruber's Contributions to the 



taking place in the main mass itself ; the humps and folds 

 gradually disappear, the pseudopodia are for the most part 

 drawn in, and with them the cones ; and after the surface has 

 become smooth, there commences a steady flow in one direc- 

 tion, exactly in the same manner as has long been known in 

 A. verrucosa^ although much slower. In the latter this stage 

 was for a time regarded as forming a distinct species under 

 the name of A. quadrilineata. 



The longitudinal folds which gave origin to this name, and 

 which are produced by the strain on the tenacious outer layer 

 acting in one direction, occur here just in the same manner 

 (tigs. 5, 6, & 7). Along them we see tlie granules hastening 

 forward in several streams, whilst a clear mass of protoplasm, 

 free from granules, in constant flow moves on before them. A 

 remarkable circumstance is that on the leading part of the 

 body pseudopodia with their cones frequently persist, and 

 thus, to a certain extent, may act as extended feelers (fig. 7). 



While at the posterior end, i. e. at the part opposite to that 

 which is pushing forward, the double contour is distinctly pre- 

 served in the outer layer, it disappears entirely on tlie ante- 

 rior part (fig. 6), from which we must conclude that the first- 

 mentioned part of the body retains its toughness, whilst 

 anteriorly all becomes in flux, i. e. the more fluid constituents 

 collect tliere. Nevertheless even these still have considerable 

 density, as is proved by the pseudopodia and pseudopodial 

 cones protruded from them, on which, however, no double 

 contour is visible. Frequently a zone of clear protoplasm 

 seems to surround the whole body ; and then the double lines 

 are no longer seen anywhere. 



Of a nucleus nothing is to be seen while the Amoeba remains 

 in the resting state and the folds of the surface obstruct the 

 view of the interior. But if the llhizopod begins to move, 

 when the body flattens itself completely, the nucleus at once 

 becomes distinctly visible (n in the figures), and appears as a 

 little disk surrounded by a narrow border, as in most Ama^bce. 

 No contractile vacuole is present, a new proof of the still un- 

 explained fact that this structure is wanting in the marine 

 Khizopoda. 



2. Amccba actinojihora^ Auerbach. 



The Rhizopod that is to be described here is a very small 

 Amccba, measuring 0'03-0'04 millim., which occurred pretty 

 plentifully in all sorts of receptacles of water in the neigh- 

 bourhood of Lindau. It excited my interest because it 

 seemed to have much in common with the Amoeba tentacidata 

 that I had previously observed ) and, in fact, it proved that it 



