466 
MONTGOMER V. 
[Vol. XV. 
substance of the vacuole stains more faintly than the ground 
substance of the nucleolus, and has much the same color shade 
as the nuclear sap. In certain germinal vesicles, which appear 
to be of a somewhat later stage of development, numerous 
small globules (j n.D ., Figs. 306 and 310) are scattered through 
the nuclear sap; they stain with eosin a little more deeply than 
the last-named nuclear portion, vary in number and size, and 
have no regular distribution. In one case (Fig. 316), which 
stood in a stage immediately antecedent to the pole spindle 
formation, where there was a centrosome at either end of the 
nucleus in the cytoplasm (the nuclear membrane had not yet 
disappeared), such globules were present in the nucleus; so 
that we may infer that these globules are one of the latest 
formations in the germinal vesicle before the pole spindle is 
formed. I have not found any stages between the stage just 
described and the perfectly formed spindle (Fig. 311). About 
fifty or sixty ova were examined in the stage of the first pole 
spindle, and in all of them the nucleolus had completely 
disappeared, and no trace of it could be found either in the 
nucleus or in the cytoplasm. 
What has been the manner of this disappearance of the 
nucleolus ? Its total disappearance must occur within a rela¬ 
tively short time, since otherwise one would expect to find 
stages showing this process. The observations which I was 
able to make would demonstrate at least the mode of the com¬ 
mencement of the vanishing of the nucleolus. We have seen 
that when the germinal vesicle has attained its greatest size 
or, in some cases, a little before its maximum size is reached, 
its nuclear sap stains red; therefore some substance must be 
suspended in the caryolymph at this period which was not con¬ 
tained in it before. Now such a substance must have been 
derived either from other elements of the nucleus or from 
the cytoplasm. It has probably not been derived from the 
cytoplasm, since the nuclear membrane at this stage has its 
maximum thickness and hence could not be easily penetrable; 
and also there is no appearance of any similar substance in the 
cytoplasm, since no yolk globules or other nutritive elements 
seem to be present, but the whole cytoplasm (at least the 
