Tae nee Meee 
1903] STUDIES IN SPINDLE FORMATION 93 
them no longer run parallel to the nuclear membrane or interlace 
with one another. They become long independent fibrils, pro- 
jecting more at right angles to the nuclear membrane and con- 
verging at the apices of the cones. Figs. 26 and 27 show 
several of these cones, nearly fully developed. 
As the cones approach the completion of their development, 
the nuclear membrane suddenly disappears, and the fibrils at the 
base of the cones come in contact with the chromosomes. The 
fusion of the cones proceeds until there are two groups (fig. 28). 
The chromosomes are very numerous, and the mature spindle is 
consequently very wide at the equator. The usual connective 
and continuous fibrils are to be distinguished, but the mantle 
fibrils do not appear until the chromosomes begin their migra- 
tion to the poles. 
It is quite clear from the series of stages shown in figs. 24 to 
29 that the formation of the first spindle in Hedera is similar to 
that which occurs in Gladiolus, Iris, Disporum, and Hesperaloe 
in every essential particular. 
In his work on Agave, Osterhout describes two distinct types 
of spindle formation in the two divisions preceding the develop- 
ment of the pollen. In the second division the spindle origi- 
nates in a way that is absolutely different from that in the first. 
There is no weft surrounding the nucleus in the early stages, but 
instead there is a series of fibrils which radiate out from the 
nucleus, with their free ends projecting into the cytoplasm. 
Such a stage as this does not occur in the first division, and it is 
remarkable that two conditions so essentially different could be 
found in two succeeding generations of cells. With the idea of 
ascertaining whether any such difference as this existed in the 
two succeeding divisions of the mother-cell in Hedera, a very 
Careful examination was made of every stage in formation of the 
Second spindle. This proved quite conclusively that the spin- 
dles of the first and second divisions are formed in identically 
the same fashion. 
Very little time elapses between the first and second divis- 
1ons. As soon as the first spindle reaches the bipolar stage, the 
chromosomes move to the respective poles and unite, forming 
