42 MONICA TAYLOR 



I have repeatedly verified the observation that such ball- 

 shaped amoebae are multinucleate. The commonest number 

 of nuclei is four, but binucleate, six- or eight-nucleate condi- 

 tions occur. The extreme rarity of mitotic figures in the many 

 preparations he examined caused Doflein (3) to leave it an 

 open question as to whether or no there was another method 

 of division. The results of my investigation lead me to con- 

 clude that the mitotic figures given by Lucy A. Carter (2) for 

 A. proteus (var. X, Carter; A. dubia, Schaeffer), and 

 by Doflein (3) for A . proteus (var. Y, Carter) are connected 

 with sporulation, and ' encystment '. The ordinary vegetative 

 multiplication, i.e. fission divisions, are effected by a sort 

 of ' budding ' of the nucleus. A search through innumerable 

 specimens at all times of the year, and at all hours of the day 

 and night, in many cultures of amoeba, some of them so 

 luxuriant that the bottom of the glass trough (8 in. in 

 diameter) appeared whitish because of the enormous numbers 

 of amoebae Ij'ing on it, has failed to give one single example of 

 a mitotic figure. It is the common experience of cytologists 

 that wherever an organism is developing rapidly mitotic figures 

 are sure to be forthcoming if such tissues be examined by 

 a suitable technique. Hence it would seem that the published 

 figures of mitosis in A. proteus belong to the sporulation 

 cycle of the life-history. 



In most of the spherical amoebae I have examined the 

 separate nuclei have been close together. If, however, the 

 spherical specimens be examined as soon as they have assumed 

 this form (and this is quite a simple matter where large numbers 

 of cultures are accessible) appearances similar to those drawn 

 in figs. 8, 9, and 14 (PI. 2) are to be found. Here the daughter 

 nuclei are clearly not completely formed, and the mother nucleus 

 is clearly not dividing by ordinary mitosis. In short, a series 

 of preparations may be made showing the gradual conversion 

 of a ' lobed ' large nucleus into four daughter products. The 



underwent a period of depression and is now (July) full of small amoebae, 

 would seem to indicate that many of the amoebae must have been pre- 

 paring to encyst. 



