THE LOBOSA 



this case the actual posterior end is not involved in the current, and 

 by the increase of surface tension becomes folded or wrinkled, giving 

 sometimes an appearance of several small pseudopodia (Fig. 12, 2). 

 In polypodious Amoebae similar reverse currents may be ob- 

 served in retreating pseudopodia, and in areas of the body 

 that are supplying materials for the axial streams of advancing 

 pseudopodia. 1 



Nucleus. The nucleus of the Lobosa in its resting condition 

 usually exhibits a well-defined membrana liniitans. The chromatin 

 is in the form of a number of spherical or irregular particles frequently 

 collected together round the periphery, leaving a more or less clear 

 space in the centre. In some cases a very delicate network of 

 fibrils has been observed, which is regarded as linin (Fig. 2). 



One or more nucleoli composed of a substance which differs 

 chemically in some of its reactions from chromatin 

 may or may not be present. 



In Paramoeba eilhardi there occurs a deeply 

 staining body in proximity to the nucleus, which 

 was termed by Schaudinn (25), who described it, 

 the " nebenkorper " (Fig. 4, c). This body divides 

 previous to the division of the nucleus, and the 

 two parts take up a position at opposite poles of 

 the spindle. This body is usually regarded as a "nucleolar cen- 

 trosome." A body corresponding to this has also been found by 



FIG. 2. 



Nucleus of Pelomyxa. 

 (After Bott.) 



m,L.- 



ch, ' 



Fio. 3. 



Dividing nucleus of 

 Amoeba Umax, m.l, the 

 meinbraua liini tans of the 

 nucleus ; c, the nucleo- 

 lar centrosome ; eh, the 

 chromosomes arranged 

 iu an equatorial band. 

 (After Vahlkampf.) 



FIG. 4. 



The resting nucleus 

 (.V) and "nebenkorper" 

 (c) of Paramoeba eilhardi. 

 (After Schaudinn.) 



Fio. 5. 



The nucleus of the 

 same species dividing. 

 The "nebenkorper" (c) 

 has divided into two 

 parts, which occupy a 

 position at the foci of the 

 central spindle, eh, the 

 chromosomes arranged 

 in an equatorial band. 

 (After Schaudinn.) 



Vahlkampf in the division of the nucleus of Amoeba Umax (Fig. 3), 2 

 but in this case the nucleolar centrosome lies within the nuclear 

 membrane. 



1 The subject of amoeboid movements has of recent years attracted the attention 

 of many observers. The views expressed by Biitschli (Investigations on Microscopic 

 Foams, etc., transl. by Minchin, 1894) have been opposed by Jennings (14), 

 but Jennings' views have been more recently criticised by Rhunibler (23). 



2 For a discussion on the nature of these bodies, see Goldschmidt and Popoff, 

 Archivf. Protist. viii., 1907, p. 321. 



