SPERMATOGENESIS OF ASCARIS 437 
have called them ‘plastidules,’ ‘plastin granules’ or ‘microsomes.’ 
Van Beneden first observed and figured them clustered around 
the chromatic mass at the center of the spermatid. But he did 
not trace their origin. Mayer first saw them in the refringent 
vesicles, and leaving these to take the position just mentioned. He 
did not trace their origin, however, and seems to have overlooked 
the fact that they always stain with acid dyes, for he calls them 
mitochondria, although all cytologists agree that mitochondria 
take basic dyes. 
When the plastochondria reach the perinuclear zone fusion 
occurs to a limited extent, resulting in fewer and larger granules, 
while many are still scattered throughout the cytoplasm of the 
spermatid. Many of these are lost when cytoplasmic reduction 
occurs. Though the diameter of the spermatid is reduced about 
one-half at this time, the granules lost seem to be only those lying 
by chance toward the periphery of the cell. There seems to be 
no selection or segregation here. 
Those that remain keep a fairly definitely symmetrical posi- 
tion around the center of the spermatid during its transformation 
into the spermatozoon, regaining it if it is temporarily lost. The 
smaller ones lie in the thin sheath of protoplasm which surrounds 
the refractive body, while the larger ones lie in the sponge-like 
protoplasm of the ‘crown’ or head (figs. 25, 27, 28 and 48). 
In these positions they are carried into the egg; but, as soon 
as they enter the egg cytoplasm, the symmetrical arrangement 
is lost, as a consequence of the absorption of the sperm cytoplasm 
by that of the egg. The larger ones in the perinuclear zone re- 
main in a fairly close group long after the outlines of the sperm 
have been lost, and can be distinguished easily by their larger 
size, as Meves has recently pointed out (’11), from similar gran- 
ules which are scattered throughout the egg cytoplasm. After 
the fusion of the pronuclei, however, they also become dispersed, 
fusing with those of the egg, or with those of there own kind, or 
remaining as small granules which take part in the formation 
of the rays and fibers of the cleavage figure. Romeis (’12) con- 
firms the observations of other authors who found that they help 
to form the fertilization membrane of the egg after they have 
dissolved in the egg cytoplasm. 
