SPERMATOGENESIS OF ASCARIS 435 
attractive force of the centrosome, arrange themselves in con- 
centric circles. The size and number of those vesicles in the 
nearest circle prevent them from coming up to the attracting mass 
at the center, so that a clear zone,—the ‘perinuclear zone’ of Van 
Beneden, is left around it. In this zone the granules just 
described stand out clearly. . 
The vesicles still stain blue in Benda’s stain, though of a lighter 
shade than before the divisions, but the granules always stain 
yellow; and, since they surround the closely massed centrosome 
and chromosomes, the red-brown of the latter is completely 
masked by the yellow, unless seen in section (figs. 12). After 
iron-hematoxylin-Bordeaux red the granules stain red, while 
the vesicles stain blue; and in Ehrlich-Biondi the granules take 
the red dye and the vesicles are purple (fig. 25). Thus these 
granules must be quite unlike the vesicles chemically. Their 
origin and history will be of interest. 
The plastosome and the plastin grains or plastochondria 
The plastosome appears in the nucleus of the spermatogonium 
very soon after division ceases. It is a small granule throughout 
the ‘rest period’ and stains yellow after Benda’s stain (figs. 3 to 
11), bright red after Ehrlich-Biondi (figs. 19 to 24) and black 
after iron hematoxylin (figs. 29, 30 and 31); while the karyochro- 
matin stains red-brown, green and blue-black respectively, after 
these stains, as shown in the figures just mentioned. 
During the synizesis stage the plastosome increases in size, 
and often small granules staining just like it are to be seen scat- 
tered throughout the nucleus (figs. 19, 20 and 21). Throughout 
the long growth period these remain evident, and their number 
increases. 
Early in the growth period small granules like those just de- 
scribed in the nucleus appear in the cytoplasm. They are very 
small, 0.1 to 0.5 » in diameter (figs. 5,6 and 7). At the close of 
the growth period, when the centrosome leaves the nucleus it 
takes these granules with it into the cytoplasm. They are often 
clustered around it in the form of a hollow sphere, as shown in 
section in figure 24. As the cleavage figure is formed, many of 
JOURNAL OF MORPHOLOGY, VOL. 24, NO. 3 
