298 Allen . — The Early Stages of Spindle-Formation 
the formation of the spindle in the Spermatophytes, and 
perhaps in the Pteridophytes as well. Such an outline 
might be somewhat as follows : — 
1. A considerable amount of kinoplasm is present in the 
cytoplasm, at least by the time of the early prophases, as 
a more or less uniformly distributed, fibrous reticulum. It 
will be important to trace still further back the history of the 
kinoplasm ; but no observations yet made seem to throw any 
light upon this problem. Indeed, very few observers have 
followed spindle-formation back even to as early a point as 
this ; but Miss Williams (’ 99 ) and Miss Byxbee (’00) find that 
the spindle primordium ( c Anlage ’) develops from an early 
cytoplasmic meshwork. 
2. The fibres of the reticulum become so arranged as to 
extend radially from the nuclear membrane out into the 
cytoplasm. It seems quite likely that this results partly from 
a radial pulling out of the meshes ; but very probably there is 
also an actual growth in length of the fibres composing the 
reticulum, so that many of them finally reach to the plasma- 
membrane. Several authors have been cited who find a 
radial arrangement of fibres at this period. 
3. As a result of a folding-over of the radial fibres, a felt 
is formed just without the nuclear membrane. 
4. The nuclear membrane and the nucleole disappear, and 
the nuclear cavity also becomes occupied by a set of fibres. 
5. The peripheral fibres of the central mass become pulled 
out to form several or many cones. 
6 . The fibres, nuclear and cytoplasmic, are gathered into 
bundles, forming a multipolar figure. 
7. The number of poles is reduced, by fusion, to two. 
The felted stage and the succeeding steps in the process 
have been so often noted that there can be no doubt in these 
later stages as to the regular course of events. Osterhout’s 
description of the formation of the cones in Equisetum by 
a grouping of radial fibres, which in turn proceed from a 
felted layer, suggests the interesting possibility of a constant 
difference in the succession of events as between Seed Plants 
