EARLY STAGES OF SEGMENTATION OF ECHINUS HYBRIDS. 493 
makes this interpretation very doubtful. When the nuclear 
membrane dissolves the figures are closely like those in the 
first prophase ; the chromosomes become scattered over the 
spindle, and, as before, some of them are seen giving rise to 
vesicles (fig. 17, a, h, c). These differ from those of the first 
segmentation mitosis only in being in general somewhat 
smaller, and in the fact that complete chromosomes appear 
less often to become entirely vesicular; the vesicles seem 
rather to be formed on the ends or sides of the chromosomes, 
and often quickly become separated from them. The fact 
that the average number of vesicles in the second division is 
about the same as that in the first, and that the chromosome 
number, as counted in anaphase, shows no further diminution, 
suggests that the same chromosomes which produced vesicles 
in the first mitosis again do so in the second. 
The division of the poles of the spindle is less conspicuous 
in the second segmentation mitosis; in anaphase they are 
often elongated transversely to the axis of the spindle, or 
divided to a small extent, but exactly similar figures are not 
uncommon in pure esculentus eggs in the same stage. The 
vesicles, as before, are scattered among or outside the chromo- 
somes, and in anaphase some are included among the daughter 
groups and enter the nucleus of the 4-cell stage ; others 
remain in the centre or round the edges of the spindle and 
are eliminated (figs. 18, 19, 20). 
Counts of late prophhase and anaphase groups gave the 
results recorded in Table III ; the prophase figures were 
counted by eye, the anaphases by drawing. As in the case 
of the first division the anaphase figures are more trust- 
worthy. Brackets on the right side of the numbers indicate 
anaphase groups of the same spindle ; on the left side 
spindles of the same egg. 
