Case of Mitotic Division in Amoeba proteus Pall. 59 
Careful examination under very high powers appears to confirm this, as 
the number of chromosomes which can be counted in Fig. la is 32, 
and in Fig. 2a is 17, bringing the number very near to 50; but the 
arrangement into jive spindles is less pronounced in Fig. la owing to the 
apparent crossing of the fibres, which is not seen under low magnifications. 
The chromosomes, if such they can be called, are small masses of 
chromatin, about 1 » in diameter; their outline is somewhat indistinct 
but apparently approximately spherical in shape. Of their progressive 
formation to build up the equatorial plate, nothing can be said with 
certainty from this one case, but there seems to be a fair agreement 
with Awerinzew’s! description of the breaking-down of the large granules 
in the resting nucleus before the appearance of the chromosomes. He 
mentions, however, a polar plate outside the nucleus, with a polar cap 
composed of the remaining nuclear protoplasm. Both these appear 
simultaneously with the differentiation of the spindle fibres. Of the extra- 
nuclear polar plate there is no evidence whatsoever in the nucleus here 
described, and while it is true that the cytoplasm surrounding the nucleus 
has been unfortunately torn away in both sections, there is no indication 
within the nucleus of any such polar plate having been present. As to 
the remaining nuclear substance, there is a certain amount all round the 
spindle next to the membrane. Within this, fragments and reticular 
strands lie diffusely scattered. The former stain with hematoxylin in 
a similar manner to the chromosomes, with which many of them agree 
in size, while others are larger. This staining material is thicker at the 
poles, and gives, on reconstruction, the impression of a polar cap containing 
the chromatin which has not been used up in the formation of the 
mitotic spindle. 
The work on Amoeba proteus, during the course of which this case of 
mitotic division has come under my notice, is being carried out partly in 
the Zoological Laboratory of the University, and partly in that of the 
College of Notre Dame, Dowanhill. 
1 A werinzew, Joc. cit. 
(Issued separately, 8rd July 1913.) 
