2 
the middle of the nucleus a central body that is composed 
of the greater portion of the cromatin-granules, whilst the 
rest of the chromatin-granules is situated in the peripheral 
network between the central body and the nuclear mem- 
brane. During karyokinesis the central body splits into 
many small ones, whilst the granules in the network increase 
in size. In this way there are formed 20 or more mostly 
loose chromosomes. À spirem is not formed. The chro- 
mosomes come to lie in a ring round the centre. The 
nuclear membrane dissolves. Then the chromosomes ap- 
proach one another, and unite into 4 to 6 tetrads or groups 
of four, which become arranged in two parallel planes, 
lying close together. The chromosomes of these two planes 
separate. No longitudinal splitting takes place. The groups 
of four now divide into smaller groups, which form two 
rings. Thereupon the central body is formed, composed 
usually of the greater number of the chromosomes. A 
nuclear membrane also appears again. Daughter nuclei 
with many tetrahedral granules, with several masses and 
with a single mass are observable. 
Eud. Escoyez!) investigated the nucleus and karyoki- 
nesis in a species of Zygnema, which he believes to have 
been different from that studied by Miss Merriman, 
but which he could not identify. 
His results are entirely different from those of Miss 
Merriman. He states that in the resting nucleus, there 
can be distinguished a network, an ordinary nucleolus 
and a nuclear membrane. Rarely there are two nucleoli 
in the nucleus. The nucleolus, according to Escovyez, lies 
in a cavity (cavité périnucléolaire) which is surrounded by 
a very thin membrane. He thinks it possible, however, 
that this cavity is formed in the fixing. He describes the 
1) Eud. Escoyez, Le Noyau et la Caryocinèse chez le Zygnema. 
Extrait de la Revue “La Cellule”, t. XXIV, 2d fasc. 1907, p. 355—367. 
