1906] YAMANOUCHI—POLYSIPHONIA VIOLACEA 429 
HARPER (39) states that, after the synaptic stage in the ascus of 
Phyllactinia, a number of strands of chromatin are attached to a 
central body, and that each strand corresponds to a single chromo- 
some. He shows that the resting nucleus of Phyllactinia has definite 
polarity. The formation of chromosomes from a strand of the spirem 
consists in the segregation of two substances present in the spirem. 
The densely staining chromatin aggregates into chromosomes, leaving 
the achromatic portion as a series of threads connecting the chromo- 
Somes to the central body, and these threads later form the spindle. 
I have studied Polysiphonia very carefully in the hope of relating its 
Process of spindle formation to that of Phyllactinia, but have not 
been able to find any essential resemblance. There seems to be no 
polarity to the resting nucleus of Polysiphonia as described by HARPER 
for Phyllactinia. 
Centrosome and centros phere-like structures—Every mitosis, no 
matter where it occurs, is characterized by the constant presence 
during prophase of two sharply differentiated centrosome-like bodies 
in the center of the kinoplasm at opposite ends of the nucleus. When 
the chromosomes are arranged in the equatorial plate the kinoplasm 
has the form of a large centrosphere-like structure at the pole of the 
spindle, and the centrosome-like bodies have disappeared. These 
structures are destitute of the astral rays, characteristically accom- 
panying typical centrosomes or centrospheres, as reported in Fucus 
(STRASBURGER 73, FARMER and WILLIAMS 32), Stypocaulon (SWINGLE 
76), Dictyota (Mortier 52, WittiaMs 81), and in animal cells. 
They have a compact, homogeneous structure in Polysiphonia, which 
makes them readily distinguishable from the surrounding protoplasm. 
The daughter chromosomes, after their separation at the equatorial 
Plate, become gathered close to each centrosphere-like structure 
at anaphase of mitosis, and in contact with it. The latter then passes 
ito a vague kinoplasmic mass which surrounds the group of daughter 
chromosomes, 
The observations summarized above, namely the appearance 
of a centrosome-like body at prophase, its progressive development 
and differentiation as a large centrosphere-like structure during 
metaphase, which is the climax of the kinoplasmic activity of mitosis, 
and its gradual decline after anaphase, lead me to conclude that these 
