io Harper and Dodge . — The Formation of the 
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formation. The spiral thickenings should really be conceived as forming 
centripetally with reference to the source of their material, just as in the 
case of the spiral thickenings in the wall of a duct or elater. Radial fibrillar 
strands are, however, not present so far as known in connexion with the 
accumulation of material for the formation of the secondary thickenings of 
ordinary cell-walls. Recent workers (42,44) have been inclined to associate 
the functions of the central spindle with the formation of the cell-plate and 
new plasma membranes rather than the cellulose wall, but the two processes 
may both be involved. If the cellulose wall is a dissociation product of the 
proteid materials of the membrane, the accumulation of materials for both 
structures should be one and the same process. 
The relations of the nuclei to the fibrillar strands and the forming 
membrane of the capillitial threads, both as to position and as to the pro- 
cesses going on, are strikingly similar to those in cell-division figures of the 
higher plants, especially at the stage when the central spindle is widening 
out to fill the whole diameter of the cell and the new fibrils for this increase 
in its dimensions are being formed. The most conspicuous difference in 
the two cases is in the fact noted, that the fibrils in the formation of the 
capillitium extend between and beyond the nuclei instead of ending upon 
them, as in the case of the central spindle. That the nuclei, on the one 
hand, and the region of deposition of membrane material, on the other, are 
iij both cases more or less definitely connected by conspicuous fibrillar 
elements in the cytoplasm must be taken as strongly suggesting that these 
fibrils represent paths for the transportation of material. 
In the case of free cell-formation in the ascus we have excellent 
evidence that the astral rays in their metamorphosis to form the plasma 
membrane of the ascospore grow in length by a process of flowage out- 
wards from the centrosome. The figures in Erysiphie communis show clearly 
enough that the whole astral system must be conceived as increasing its 
extent by the addition of material from the region of the centrosome, and 
that the latter, with its direct connexion with the chromatin through the 
nuclear beak, may well be characterized as a point of interaction between 
the nucleus and the cytoplasm, at which kinoplasmic material is formed (21). 
It is quite clear that the kinoplasmic material must increase in amount if it 
is to form a complete boundary for the spore, and the blue-stained 
boundary layer is at first thicker round the centrosome, and only gradually 
thins out by the flow of its material over the opposite pole of the spore. 
Fraser (13) accepts the conception of the centrosome as the point of 
origin for the material which forms the boundary of the spore, and charac- 
terizes the rays as direct currents set up in the cytoplasm about the centro- 
some. Later, Fraser and Welsford (14) advance the conception that the 
material formed at the centrosome is of the nature of an enzyme. Fraser 
rejects the comparison of the rays in the ascus to cilia, but there is cer- 
