PROTOZOA. 27 



specialized than the colored nucleus of A. proteus (PI. 9, 

 fig. 4) . Inside of the dark colored outer layer is a zone 

 of nuclear sap, while the central mass we may probably 

 indicate as a nucleolus. 1 In PI. 12, fig. 2, four of the 

 twenty-four nuclei are in the process of division, and the 

 figure is very instructive as showing the origin of the 

 many-nucleated forms. The process is probably rapid, 

 and this may account for the fact that few naturalists 

 have been fortunate enough to observe and draw it. 



In Pelomyxa palustris Greef we have an Amoeba-like 

 form when young' 2 (PI. 13, figs. 1-4). Many of these 

 Amoebae came from a dead Pelomyxa. After moving 

 about, they became more quiet (PI. 14, fig. 5), some con- 

 tracted themselves into a spherical or pear-shaped body 

 (PI. 13, figs. 6, 7), after which a long vibrating thread was 

 stretched out (PI. 13, fig. 8), and the Amoeba became 

 transformed into a flagellate animal. After rapid rotat- 

 ing movements this young flagellate organism passed out 

 of sight, "rowing with the front, quickly swinging whip," 

 so that unfortunately its further development was not 

 observed. Whether the flagellate young remained a flag- 

 ellate organism, or whether it passed into the unflagellate 

 adult (PL 13, fig. 9) cannot be stated. In the adult, the 

 tendency towards an anterior and a posterior region of 

 the body is marked. The animal stretches itself out and 

 moves in curves, turning the forward end, now to the 

 right, now to the left (PI. 13, fig. 9). At the posterior 

 end there is a glassy disc-like expansion. PI. 13, fig. 10, 

 is a magnified portion of the body. Many nuclei are 

 present which may be converted into the "shining bod- 



iGruber, Zeitschr. f. wiss. Zool., XXXVIII, 1883. According 

 to Calkins, the Protozoan cell, with possibly one exception, has no 

 true nucleolus comparable with the nucleolus of the Metazoan cell. 

 What has been so called is, according to this author, either func- 

 tional chromatin that has aggregated into a mass, or an intranuclear 

 sphere or division center (see The Protozoa, 1901, p. 253). 



2 Greef , Arch. f. mikr. Anat., X, Supplement, 1874, p. 51. 



