OVARY AND OVARIAN EGG OF ANOPHELES 419 
branches. The progressive stages of the branching are seen 
in figs. 1-6, which are reconstructions made from serial sections. 
In individual sections the branching nature of the nucleus 
cannot be seen, as only sections of the branches are found 
and these appear to be fragments of the nucleus, as described 
by S. R. Christophers (2). 
Besides altering in form the nucleolus undergoes an altera- 
tion in structure. Shortly after the branching has commenced 
the vacuoles of the outer crust become indistinct, and the 
central mass, which up to this point has not taken up stain, 
now becomes darker and the whole becomes very granular 
(fig. 19). Later the whole of the products of the nucleolus 
form a homogeneous granular mass which readily takes up 
nuclear stains. ‘The branches of the nucleus are entirely 
formed of this mass and, in the earlier stages at least, are 
surrounded by the nuclear membrane. 
As the branching proceeds the branches become finer and 
finer, and pass throughout the whole of the rapidly enlarging 
oocyte. They have, however, a very definite arrangement. 
It will be seen in figs, 22 and 23 that the main branches occupy 
approximately a median position between the centre of the egg 
and the periphery, forming a cup-like structure roughly 
following the contours of the egg. It must be pointed out, 
however, that in these two sections the nuclear branches 
appear much more continuous than is nermal, though indica- 
tions of this arrangement can be seen in all sections of this 
and later stages. The thickenings of the ring-shaped nuclear 
mass in fig. 22 are the main branches cut transversely, and 
the thin portions joining them are smaller lateral branches ; 
these appear to connect the larger branches together, so that 
probably the nucleus forms a reticular structure from which 
thin short branches pass towards the centre of the oocyte, 
while others go towards the periphery. The reconstructions 
do not show this reticular structure of the nucleus, but this 
may be accounted for by the fact that only the very finest 
branches appear to join the main branches together, and I found 
it impossible to reconstruct the course of such fine branches with 
NO. 259 Ff 
