282 Allen. — The Early Stages of Spindle- Formation 
the spindle, with the poles. The number of poles is reduced 
to two, possibly by fusion, resulting in a typical bipolar 
spindle. Belajeff’s observations of Lilium and Fritillaria 
pollen-mother-cells agree, so far as they go, with those of 
Larix. A dense intra-nuclear network is formed ; then knots, 
possibly, he thinks, centrospheres, appear at various places 
in the cytoplasm, from which fibre-bundles penetrate the 
nuclear membrane and attach themselves to the chromosomes. 
The membrane disappears and a multipolar figure is formed, 
which passes into a bipolar spindle. 
Strasburger’s (’95) description of some stages of the same 
division in the pollen -mother-cell of Larix europaea corro- 
borates that of Belajeff as to the felted stage, the disappear- 
ance of the nuclear membrane, the formation of a central 
fibrous system, a multipolar and finally a bipolar spindle. 
Nemec (’98 £) describes quite differently spindle-formation in 
Z. decidua (Z. europaea , DC.). He finds an early stage of 
cytoplasmic radiation, succeeded by an aggregation, just with- 
out the nucleus, of granular material, sharply separated from 
the much-vacuolated outer cytoplasm. Next to the mem- 
brane appears a hyaline region, which grows at the expense 
of the granular zone. In the hyaline layer appears a 
reticulum ; this develops into a system of fibres, which orient 
themselves into a multipolar figure. Fibres also appear 
within the nucleus, the membrane disappears, and from the 
whole fibre-complex a bipolar spindle is developed. 
Belajeff was the first to interpret a multipolar as a stage 
in the development of a bipolar spindle ; but Strasburger (’80) 
had, some years earlier, figured a tripolar spindle in the 
endosperm of Reseda , and had described similar figures in 
Ornithogalum and Leticojum. Later, he (’88) figured the 
spindle in Leucojum ; also a multipolar spindle in the 
equatorial plate stage from the endosperm of Allium , whose 
great number of chromosomes led him to explain it as due to 
a fusion of several nuclei. A felted stage, similar to that 
described by Belajeff, had been found by Strasburger (’88) in 
Leucojum . 
