1903] STUDIES IN SPINDLE FORMATION 87 
for instance, those that are connected with the chromosomes, 
those that extend from end to end of the spindle, and those 
that extend laterally outward with their free ends projecting 
into the cytoplasm. These are known as the connective, con- 
tinuous, and mantle fibers respectively. 
The spindle having now reached the bipolar condition, and 
the connective fibrils from the respective poles having become 
connected with the chromosomes (figs. ro, zr), the latter bodies 
take up their characteristic position at the equator, and the for- 
mation of the spindle is complete. 
The series of events leading to the formation of the spindle, 
as here described for Iris, agrees in every essential detail with 
those which occur in Gladiolus. 
THE POLLEN MOTHER-CELLS OF DISPORUM HOOKERI. 
The anthers and pollen mother-cells of Disporum are not as 
large as many other liliaceous types that have been used for the 
study of spindle formation ; nevertheless, they form an extremely 
interesting subject. When properly fixed in the field, the various 
stages in the formation of the first spindle of the mother-cell may 
be readily obtained. 
In the resting condition of the mother-cell, the nucleus is 
centrally situated, but as division approaches it is invariably 
found near one side. Before any kinoplasmic differentiation 
takes place, the chromatin has broken up and assumed the 
form of definite spherical chromosomes, of which there are but 
eight. The first evidence of spindle formation is to be found 
in the transformation of the cytoplasm in the immediate vicinity 
of the nuclear membrane. At first, this change takes place in 
much the same manner as described above for Iris. There are 
in the beginning but a few short threads, which when followed 
outward are found to be continuous with the reticulum of the 
Surrounding cytoplasm, but they have lost the granular char- 
acter and stain blue with the gentian violet. These threads 
increase in number and gradually form a distinct weft, which 
appears to form more abundantly on one side of the nucleus 
than on the other; that is, it is much more evident on the side 
