V'l SYNOPTIC COLLECTION. 



From this point of view the Amoeba is interesting as 

 offering an intermediate position between organisms that 

 are absolutely unprotected, like Protamoeba and others, 

 and those that are permanently covered with hardened 

 protoplasm or with a chitinous or a calcareous shell. 



Within the endosarc is a nucleus (fig. 3, white ; fig. 4, 

 the same colored) which consists of a nuclear membrane, 

 nuclear fluid, often called sap, and suspended in the latter 

 a large number of grains which allow themselves to be 

 colored and are therefore called chromatin grains. The 

 non-contractile vacuoles are present, and also a contractile 

 or pulsating vacuole, or vesicle, as it is often called (fig. 

 3, pink in color) which is more or less constant in posi- 

 tion, and which may have arisen phylogenetically from 

 the former, as suggested by Haeckel. 1 



Besides the vacuoles, nucleus, and minute crystals that 

 are often found in the protoplasm, there are grains of 

 sand which the animal has taken up in crawling over sur- 

 faces, but which it has not formed into an outer covering 

 or shell. The pseudopodia are blunt, like those of Pro- 

 tamoeba, and are extended in the act of performing the 

 function of locomotion (fig. 5). This figure shows also 

 the transient tendency to an anterior and posterior region 

 of the body which is sometimes observable. The Amoeba 

 is a crawling type, although now and then it floats and 

 swims. At such times its body becomes rounded and its 

 pseudopodia radiate in different directions, as seen in fig. 

 6, which illustrates clearly the correlation of structure and 

 habit. The power of taking food is finely shown in figs. 

 3 and 7. In fig. 7 a pair of pseudopodia, acting like the 

 finger and thumb of the human hand, have come together 

 at their ends, entirely encircling an active Infusorian, 

 Urocentrum. Another recently captured Urocentrum is 

 seen within the body of the Amoeba. In fig. 3, a diatom 



ijena. Zeitschr., IV, 1868. Engl. transl, Quart. Journ. Micr. 

 Sci., IX, 1869, p. 1 14. 



