256 Uni'versitij of California Publications in Zoology [Vol. 16 



However, the position of the spindles and the outline of the cytoplasm 

 indicate that that would be the case. That some kind of cytoplasmic 

 division must sometimes take place is evident from the fact that the 

 amoebas found in my cultures rarely had more than three nuclei, at 

 most only four, while two and three spindles are of most common 

 occurrence. The multinucleate condition evidently comes from eases 

 in which the cytoplasm failed to divide after mitosis. 



Figure 21, plate 19, shows an amoeba with two reorganizing nuclei. 

 From the position of the upper nucleus it does not seem probable that 

 the two are daughter nuclei, but that they came from nuclei which 

 formerly had their spindles nearly at right angles to each other but 

 the upper one of which had been shifted by movement. In this case 

 there may have been a recent plasmotomic division such as might part 

 the upper from the lower half of the four-nucleate plasmodium shown 

 in plate 19. figure 26. 



5. Budding 



Two types of budding, exogenous and endogenous, occur as a method 

 of asexual multiplication in the life-history of this species of amoeba. 

 In the first the bud is con.stricted off at the periphery of the cytoplasm 

 and has chromidia but no definite nucleus at the time it is separated 

 from the parent individual. In the second, the bud is constricted off 

 within a vacuole in the cytoplasm and contains a typical nucleus. 



In the process of multiplication by exogenous budding, the periph- 

 eral lobes of cytoplasm are constricted off. each containing chromidia 

 given off by the nucleus. These chromidia then reorganize to form 

 nuclei of the new small individuals in which later coincident growth 

 of nucleus and cytoplasm ensues. 



Exogenous budding has been found in a few cultures, whose con- 

 ditions are not noticeably different from those of other cultures. In 

 the individuals in which this form of multiplication occurs there are 

 noted small karyosomes (1.5/x,), heavy peripheral chromatin and 

 chromatin granules or chromidia in the cytoplasm. The kaiyosome is 

 either less deeply stained than that of the u.sual resting nucleus, or it 

 has its chromatin all at the periphery (pi. 19, figs. 33, 34). In the 

 living forms a tendency to round off portions of the cytoplasm at the 

 periphery may be observed. In the buds there is not a distinct nucleus, 

 but several small chromatin granules or chromidia. Later, judging 

 from the decrea.se of the chromatin of the karyosome and its appear- 

 ance at the periphery, the chromidia are formed at the expense of 



