288 Allen. — The Early Stages of Spindle-Formation 
been found in species representing diverse groups, and it is 
generally recognized that a method of spindle-formation 
accompanied by the activity of a centrosome is at least of 
widespread occurrence among the lower plants. 
As we have seen, there is much uncertainty and variance 
in the accounts of different authors as to what takes place 
in the early history of the spindle in the higher plants, previous 
to the appearance of the extra-nuclear felt. Besides, the 
presence of centrosomes, though rendered extremely im- 
probable, is not admitted by all writers, at least, to be 
entirely excluded by known facts as to the multipolar origin 
of the spindles. For these reasons, special attention has been 
paid in the present investigation to the early prophases of 
mitosis, and an attempt has been made to follow closely the 
history of the cytoplasmic structures in these stages. The 
problem here involved is a purely physiological one, and 
the description of structures occurring in isolated stages of 
karyokinesis is by no means sufficient for its solution. A 
complete series of stages, showing the changes actually going 
on within the cell, must be studied, and their connexion shown. 
From this point of view, much of the discussion regarding the 
presence or absence of f centrosome-like granules’ at the 
spindle-poles is seen to be useless. There can be no doubt, 
from the citations already given, that granules or larger masses 
are often to be found at the poles ; but nothing can be 
determined as to the significance of these bodies until the 
complete history of the spindle has been traced. 
Original Observations. 
The following description applies to the first nuclear division 
in the pollen-mother-cells of Larix europaea , DC. Male 
cones were fixed at various times during the fall, winter and 
spring, both from material just taken from the trees and from 
that whose development was hastened by keeping it for from 
one to four days in a warm room. Strasburger (’00, p. 68) 
finds that material forced in this way yields the same karyo- 
kinetic figures as that which has developed more slowly 
