464 Sargant . — The Formation of the 
chromosome however is interesting, since it recalls the struc~ 
ture of the corresponding stage in the spermocyte of Ascaris 
megalocephala. Here also Dr. Brauer has traced the four rows 
to a double longitudinal fission h 
The two nuclei which now occupy the embryo-sac (Fig. 26) 
soon show signs of approaching division. They increase in 
size, and the ragged-looking network characteristic of the 
resting state gives place to a neat spirem ribbon. Some 
preparations show this ribbon clearly bordered on either side 
by a row of dark dots. It very soon becomes of a uniform 
colour. At first both nuclei possess a nuclear membrane and 
nucleoli, and even at this early stage a difference in size 
between them may often be observed (Fig. 27). The chalazal 
nucleus is commonly larger than that at the micropylar end. 
Both nuclei are sometimes surrounded by a comparatively 
clear space divided from the cytoplasm by a granular boundary 
(Fig. 27). After disappearance of the nuclear wall this clearer 
space persists, and well-marked radiations are found in it. 
A washy nucleolus can still be perceived among the tangled 
chromatic coils (Fig. 28). 
Segmentation of the naked spirem ribbon takes place while 
it is still much tangled and of irregular breadth (Fig. 29). 
The spindle-fibres have appeared and seem to stretch the 
figure in one direction, so that the young chromosome is 
much pulled out in that part which lies along the spindle- 
fibres and twisted or knotted at the free ends. By degrees 
the chromosomes contract to uniform breadth, though their 
ribbon-like character is still apparent. The spindle has also 
become better defined and more regular, and each chromosome 
lies on it with one end in the equatorial plane, the other 
extended to one of the poles. 
The chromosomes can now be counted at least roughly, 
and the well-known distinction between the nuclei becomes 
apparent. There are about twelve chromosomes in the micro- 
pylar nucleus, but commonly not less than twenty-four in the 
1 Brauer, Zur Kenntniss der Spermatogenese von Ascaris megalocephala 
(Fig. 25). 
