» SPERMATOGENESIS OF ASCARIS 431 
times the central mass is temporarily pushed aside (fig. 37). 
Fusion continues, however, until a single hemispherical body is 
formed which comes to lie in the cytoplasmic cone of the sper- 
matid, stretching the latter until it forms a mere sheath around it 
(figs. 15 and 38). The refractive mass now elongates, taking the 
form of a truncated cone. Its base is slightly concave, and 
adjoins the clear zone, which has regained its former position 
(fig. 48). 
The refractive body is now completely formed. Before the 
fusion of the refringent vesicles begins sections of them show 
a different reaction to stains on the surface and in the interior. 
This difference is very marked in sections of the globules and of 
the refractive body itself. While the surfaces of all these in- 
clusions remain a deep blue after Benda’s stain the interiors of 
them become more and more yellowish as fusion progresses, and 
finally the entire inner portion of the refractive body stains yel- 
low. In the older spermatozoa even the surface of this body 
loses the blue color (figs. 12, 15, 16 and 25).° 
I believe this is the final step in the history of the blue-staining 
material, or karyochondria, in Ascaris; that it is entirely con- 
sumed in the formation of the refractive body of the spermatozoon 
by changing chemically into the material of which that body is 
made, namely, yolk. 
For we know that all secretions whether glandular or yolk, 
stain yellow after Benda’s stain. Indeed, Bouin (’05) considers 
the growing spermatocyte homologous with the gland cell so 
far as the secretion of yolk in it is concerned. We know that in 
many gland cells a substance appears in the cytoplasm just be- 
fore secretion begins, and gradually disappears as the secreted 
material accumulates (Faure-Fremiet, 10, for literature). This 
substance has been called a ‘prezymogen’—a factor which directs 
secretion, and may later transform into the secretion itself. In 
other forms this factor is known as ‘mitochondria,’ and its be- 
havior seems to be followed precisely, as we have seen, by the 
karyochondria in Ascaris. Mitochondria, however, are consid- 
ered to be wholly cytoplasmic in origin. 
6 Romeis (12) confirms this observation. 
