160 THE CHROMOSOMES 
thin threads next assume the form of loops with their 
free ends pointing toward one pole, e (bouquet 
stage, also called the period of synapsis). At their 
free ends the threads soon appear to meet in pairs, 
d and e. Each pair, by the apparent fusion of its 
threads, leads to the formation of a thick thread in 
the form of a loop, f. Further condensation and 
separation of the threads leads to the condition shown 
ing. The thick double threads next show a length- 
wise split, the halves being often twisted around 
each other (diplotene stage) h. The pairs of threads 
now begin again to become longer and to occupy 
more of the interior of the nucleus as seen in 7. The 
eggs have grown larger meanwhile and the yolk 
appears. As the nucleus grows still larger, keeping 
pace with the growth of the cell, the chromosomes 
begin to lose their staining capacity. Despite the 
difficulty of tracing the chromosomes throughout the 
remaining period, Maréchal has succeeded in follow- 
ing them, step by step. His drawings of the chro- 
mosomes give the impression of the existence of a 
central core or filament remaining, as shown in 
Fig. 44 2, 7, k&. Delicate loops and threads are 
attached to this core and may be traced out into the 
region of each side of the chromosome. During 
these stages deeply staining balls of material, the 
nucleoli, appear in the nucleus. Finally the chro- 
matin threads begin to condense again and once 
more take the stain; the chromosomes are found lying 
in pairs often twisted around each other as before, as 
seen in 7. They pass in this condition on to the first 
