480 Mr. L. Doncaster. [Jan. 25, 
clumped together, and may give the appearance of about 10 or fewer very 
thick chromosomes. If care is not exercised such figures may be mistaken 
for haploid mitoses, but a little experience at once shows the difference, 
and usually in other parts of these eggs undoubted diploid mitoses may be 
found. 
In all these cases no polar chromosomes can be found in any egg of the 
series to which they belong. 
In the eggs of the haploid type the behaviour of the nucleus does not 
differ from that described until it has become flattened against the edge of 
the egg, and has then begun to swell, so that instead of being an evenly 
stained body it takes the form of an oval vesicle in which chromatic masses 
are distinguishable. Instead of sinking into the egg it continues to enlarge 
at the edge and occasionally a stage may be found in which the chromatin is 
ageregated at the two sides of the nucleus, one mass being next to the edge 
of the egg and the other towards the inside (fig. 11). As was deseribed in 
the previous part, both for the summer and spring eggs, no regular equatorial! 
plate has ever been found. The next stage, of which I have a number of 
examples, shows the chromosomes separating into two groups; an inner in 
which they appear as a group of parallel rods as in an ordinary anaphase, 
and an outer in which they are very irregularly arranged in a loose group 
close to the edge of the egg. 
In some sections of this stage (fig. 12) it can be seen that the inner group 
of parallel chromosomes is in the equator of an elongated mitotic spindle, 
and although I have no very clear figures of these stages, those which I have 
suggest that the rod-like chromosomes divide transversely, giving rise at the 
inner end of the spindle to the egg-nucleus, at the outer end to a second 
group of polar chromosomes (fig. 13, a, 6, cf. Plate 3, fig. 42 of first part of 
this paper). | 
In this way a large outer and smaller inner group of polar chromosomes 
arise, and during the segmentation stages two groups are often found, one of 
which frequently contains about 10 chromosomes. In other cases the outer 
group appears to divide into two, both of which are irregular and can never 
be counted with accuracy. Fig. 14, a, >, represents the only case in which 
I have found this division taking place. On the whole it is clear that the 
polar divisions of the spring eggs which undergo maturation do not differ 
widely from those of the summer eggs, which require fertilisation, as 
described in Part I. There is in both essentially a double polar division, in 
the first part of which an irregular outer group of chromosomes separates 
from a more regular inner group, followed immediately by the division of the 
inner into egg-nucleus and inner polar group, each of which contains the 
