STUDIES ON GERM CELLS 5a 
pis, although in this form the rods which condense seem to con- 
sist of single instead of double chromosomes (fig. 66). The 
history of the nucleus as recorded by Martin is as follows: 
The chromatin in the very young oocyte is aggregated. at the poste- 
rior side of the nucleus. As the oocyte grows, it spreads throughout 
the nucleus, forming numerous granules which are distributed upon a 
reticulum. Chromosomes are than formed and soon become arranged 
on aspindle, which becomes more and more compact until a single mass of 
chromatin results (fig. 67). This mass divides in polar body formation 
(fig. 68) apparently without the presence of spindle fibers or asters. 
The germ-line-determinants in Copidosoma. The ‘nucleolo’ or 
germ-line-determinant appears in my material at about Stage D 
(fig. 49) at which time it is perfectly distinct, staining a deep 
black in iron hematoxylin. From this stage on it is invariably 
present, increasing in size until Stage F (fig. 51) is attained. 
Five methods of origin have been suggested for this body. (1) 
Silvestri’s (06) first idea that it consists of the nucleolus of the 
germinal vesicle was shown to be incorrect in my preliminary 
report (Hegner ’14 b) and Silvestri has admitted his error (Silves- 
tri 714). (2) My conclusion that it arises from the chromatin 
of the oocyte nucleus has on the other hand been disputed by 
Silvestri and I wish here to acknowledge the truth of his obser- 
vations. (3) In his latest report Silvestri (14) coins a new name 
for this body, calling it the ‘oosoma,’ and thinks that it may 
possibly arise from a heap of granules at the posterior end of 
the nucleus (fig. 69). (4) Martin accepts Silvestri’s term 
‘nucleolus’ for the body, but claims that in Ageniaspis it is gradu- 
ally built up by the aggregation of granules which appear in the 
cytoplasm of the posterior region of the egg (fig. 70). (5) Since 
.I have been unable to confirm with my material either of the 
methods of origin suggested by Silvestri and Martin and since 
this germ-line-determinant appears suddenly at about Stage D 
(fig. 49), I wish to propose another theory as to its genesis. In 
Part II of my series of “Studies on germ cells’ (Hegner ’14 a) 
I have expressed the following conclusion, after collecting and 
discussing all the literature on the origin and history of the 
germ-line-determinants in animals. 
