7 
Davis . — Spore Formation in Derhesia. 
periphery are actually connected with the outer plasma membrane (Fig. 15). 
About one-third or one-fourth of these strands may be so connected, while 
the remainder, as before, radiate out into the cytoplasm between the plastids. 
At this time granules may be found on the strands at various distances 
between the nucleus and the plasma membrane (Fig. 15). The sharpness 
of the granules indicates that they are organized bodies travelling along the 
strands, which become arranged in a funnel-shaped form with the broadest 
region of the funnel at the periphery of the cell. It is, however, possible 
that what appear to be granules are in the living cells merely thickenings of 
the strands, and that material moves outwards from the periphery of the 
nucleus through the strands in a semifluid condition and not as granules ; 
but the sharpness of form and depth of staining of these structures indicate 
that definite granules are actually present. The appearance of the funnel- 
shaped arrangement of the strands in relation to the nucleus when viewed 
from the interior of the zoospore is shown in Fig. 1 6. The granules 
accumulate in a circle just underneath the plasma membrane where they 
later form the blepharoplast. The funnel-shaped group of strands connect- 
ing the nucleus with the periphery seems to exert a pull on the plasma 
membrane so that it is drawn inward as a slight depression or shallow 
groove. 
The granules gradually appear more numerously in the circle just 
underneath the plasma membrane and with the nucleus lying below (Fig. 17). 
A portion of such a circle, viewed from the interior of the zoospore, is 
shown in Plate II, Fig. 18. The granules then fuse with one another 
to form a ring, which becomes the blepharoplast, staining very black with 
haematoxylin, and so firm in texture that it may be sharply cut with 
the microtome knife. Its appearance when viewed from the surface of the 
zoospore is shown in Fig. 19. The strands connecting the nucleus with the 
developing blepharoplast become less conspicuous and finally disappear 
after the blepharoplast is formed, leaving the boundary of the nucleus 
nearest to the plasma membrane without conspicuous radiations. The 
nucleus then passes from the periphery back to the centre of the zoospore, 
and the plastids become distributed around it as before in a radiating 
arrangement (Fig. 20). The plastids also encroach into the region of the 
zoospore just under the blepharoplast from which they had previously been 
excluded by the funnel-shaped group of protoplasmic strands. 
The blepharoplast when first formed is a single ring as shown in cross- 
section (Fig. 21 b ). It lies very close to the outer plasma membrane, but is 
not a part of it. The blepharoplast now splits into two rings, one below the 
other, and the circle of cilia grows out from the lower (Fig. 22). The split- 
ting of the primary ring is a gradual process. The ring changes its form so 
that in cross-section it appears somewhat U-shaped with the arms of the U 
very much thickened (Fig. 23 b). The two thickened portions then separate 
