436 EDWARD E. WILDMAN 
the granules scatter throughout the cytoplasm, and these cannot 
be distinguished by size, form or staining reaction from those 
already there. 
At about this time one finds similar granules inside the refrin- 
gent vesicles, as stated above. The plastosome itself sometimes 
survives the growth period as a unit, though often it does not. 
It is never found in the spermatid nor the spermatozoon, but in 
both of these the plastochondria are very conspicuous. Usually 
it exists only as scattered fragments by the time the maturation 
divisions occur, and these form the rays and fibers of the cleavage 
figure. Whether these plastin grains or plastochondria reach 
the cytoplasm by passing through the nuclear membrane at 
many points, or by going out with the centrosome they are 
undoubtedly of plastosomal origin and nature. 
But some of these granules develop within the refringent ves- 
icles, escaping from them just after the second maturation divi- 
sion. These cannot have come from the plastosome. Yet their 
staining reactions indicate that they are exactly like all the other 
plastochondria. We have, apparently, in this observation, a 
proof of the true origin of all of the plastochondria, and so of 
the plastosome itself. Their staining reactions, whether within 
or outside of the nucleus, show them to be secretion or excretion 
products. Here we see what substance it is which first secretes 
and then excretes them. In the cytoplasm the only secreting 
agent is the karyochondrial material in the form of the refrin- 
gent granules and vesicles. In the nucleus the plastosome does 
not appear until this material is present in considerable quantity. 
I believe we must conclude that the plastosome and its derived 
plastochondria, therefore—indeed, the plastochromatin in all its 
various forms—arises in the karyochromatin as a product of its 
metabolism. Montgomery (’11) reaches this same conclusion, so 
far as the origin of the plastosome is concerned, from his study of 
the history of the nucleus of the spermatocyte of Euchistus. 
That the plastochondria cannot be used as food by the sperma- 
tozoon is shown by the fact that they are excreted by the refrin- 
gent vesicles just before these fuse to form the refractive body, 
which is the food supply of the spermatozoon. Earlier authors 
