TETRAD AND EMBRYO-sAC MITOSES 79 
THE SECOND Division 
During the prophase of the second division in the embryo-sac- 
mother-cell delicate radiating fibers in great numbers are found 
surrounding the nucleus and extending from the same in all direc- 
tions (pl. zz, fig. 42). In certain cells where the walls come into 
contact with the nucleus these fibers then appear in sections as if 
there were two distinct systems arising from the opposite sides 
of the nucleus. They thus simulate asters. In point of fact, how- 
ever, they form a zone about the nucleus lying parallel to the com- 
pressing cell walls (p/. zz, fig. 15).. 
Such radiations have been figured and described by many 
authors, but accounts are, in spite of a multitude of detail, still in 
such a condition as not to warrant us in believing that we as yet 
understand fully the relation between the nucleus and these radia- 
tions. 
Their resemblance, however to certain appearances is parthe- 
nogenetically developing eggs of Zoxopneustes after treatment with 
magnesium chloride has led Wilson * to make the following sug- 
gestion which I give in his own words. 
“The formation of a perinuclear zone in the magnesium eggs 
strongly suggests the accumulation of ‘kinoplasm’ about the 
nucleus in the early prophase of cell division in the higher plants, 
as described by Osterhout and Mottier, and a number of later 
observers, though the later phenomena are in many respects very 
different.’ 
According to Wilson’s direct observations on the living Mg- 
eggs, a primary radiation appears surrounding the nucleus and 
extending far out to the periphery of the cell. “This radiation is 
interpreted as a flow of hyaloplasm which, in part at least, gives 
rise to the appearances making up the “aster.” . The gradual dis- 
appearance of these radiations is accompanied by the formation of 
a clear perinuclear zone, followed by “enlargement of the nucleus 
and the disappearance of the nuclear membrane accompanied by a 
reduction of the rays almost to the vanishing point." (4 c.) 
The comparison is strengthened by the facts described earlier 
۶ peine Studies in Cytology, I. A cytological Study of artificial Parthe- 
nogenesis in Sea-Urchin Eggs. Archiv Entwickelungsmechanik der Organismen. 12: 
