168 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
is independent of the concentration of the chromatin. No centrosomes 
or radiations have yet appeared in connection with these germinative 
vesicles. Before the chromosomes begin to form, the germinative 
vesicle becomes smaller, and often ellipsoidal, and the cytoplasm forms 
a special zone about it (Figs. 5, 6).. The conditions shown here, 
especially the presence of the cytoplasmic envelope, are those which 
immediately precede the formation of the maturation spindle, for they 
occur during the following stages (Fig. 7) when the spindle is forming, 
but are not present in the earlier germinative vesicle (Figs. 3, 4). It 
should be said that the ellipsoidal shape of the germinative vesicle 
may be found some time before the spindle appears, eggs killed ten 
hours before the time of discharge sometimes having this form (Fig. 2). 
Figures 5 and 6 show only a slight concentration of the chromatin, 
and. neither centrosomes nor radiations. ‘The next older stage found 
(Fig..7) already possessed centrosomes with well marked astral rays 
in' the cytoplasm, and the maturation spindle was beginning to be 
formed. ‘lhe cytoplasmic envelope surrounding the germinative 
vesicle was less evident than in the preceding stage. ‘The membrane 
of the vesicle was deeply indented. opposite one aster, and slightly so 
opposite the other. ‘This may be taken as evidence that the matura- 
tion spindle is formed, in part at least, from the cytoplasm, and that it 
may aid in the dissolution of the nuclear membrane. 
The next stage which I have found shows the first maturation spindle 
with the chromosomes at its equator. In this stage the spindle is 
approximately tangential to the nearest point of the surface of the 
egg, though one pole is sometimes a little closer to the surface of the 
egg than the other. The polar radiations are less distinct than form- 
erly, though the centrosomes are still present. Both centrosomes and 
radiations were at first overlooked, and in a previously published note 
(G. T. Hargitt, :09) they were stated to be absent. Figures 8a, 8b, 
9a, 9b, 10a and 10b are nearly polar views of the equatorial-plate region 
of three eggs, the chromosomes in each case extending over two sections. 
Figure 11 (Plate 2) is a similar view of a fourth egg, though here the 
chromosomes occupied three sections. In Figures 9 and 10 several of 
the chromosomes are seen to be in the tetrad condition, and a splitting 
of. some of them seems to have begun. Others appear as short rods, 
but are so small that the direction in which the division occurs cannot 
be accurately determined. . Figure 11, however, makes this somewhat 
clearer. Here are found bodies in rod-, x- and y-shaped conditions, 
as. well as some which have a roundish or irregular form. ‘The im- 
pression made by the appearance of the chromosomes is that the rods 
