ELERY R. BECKER. 



locomotion of amoebae. It was for this reason that the writer 

 undertook the experiments reported in this paper. The amoeba 

 employed throughout was Amoeba dubia which is characterized 

 by an ovoid nucleus, lack of ectoplasmic ridges, and the possession 

 of many pseudopods, with no axial pseudopod. Thanks are due 

 to Dr. J. A. Dawson for giving assistance in way of amoebae and 

 technique in starting the cultures. After the cultures were once 

 well started, little difficulty was experienced in carrying them on. 



From their figures, it appears that Hofer used the type of 

 amceba with the ovoid nucleus, possibly A. dubia, while Stole 

 used an amceba with a biconcave nucleus, probably A . proteus or 

 A. discoides (See Schaeffer, 1916). The others employed "A. 

 proteus," but from their figures it is impossible to determine 

 which species of the proteus types. 



The instrument employed in my experiments in removing the 

 nucleus was a fine, hard glass point drawn out in a micro-burner, 

 by means of which the portion of the amceba containing the 

 nucleus was severed from the remaining portion. In all cases the 

 enucleated portion was slightly larger than the nucleated. Each 

 portion of the amceba was then placed in a watch glass in a large 

 drop of fluid from a culture in which amcebae were actively 

 growing, and kept in a moist chamber for observation. The 

 water was changed twice daily so as to be kept as fresh as possible. 



Records were kept of sixty-four enucleation experiments, 

 although many more were performed with similar results. The 

 length of life of the enucleated fragments was somewhat variable, 

 as follows: 



Two amcebae lived only one day; eleven, two days; eighteen, 

 three days; sixteen, four days; eleven, five days; four, six days; 

 one, seven days; and one lived eight days. Thus the greater 

 number lived between three and four days. This may be com- 

 pared with Hofer's enucleated amoebae which lived from eight to 

 twelve days (one more than fifteen days) and those of Lynch 

 which lived for from six to eight days. Stole claims to have 

 been successful in keeping amcebae artificially enucleated alive 

 for as much as twenty-five days. Strangely enough, however, two 

 enucleated fragments which arose from two different amcebae 

 that had divided spontaneously lived only ten and four days 



