Helen Dean King 353 
be very remarkable if some of the threads did not lie parallel for a 
longer or a shorter distance. 
During the growth stages and until the formation of the first matura- 
tion spindle the centrosome is always to be found in the portion of the 
cell containing the greatest amount of cytoplasm (Fig. 15). As in 
the resting spermatogonia the centrosome is surrounded by a granular 
attraction-sphere which always appears homogeneous. The acroblast 
can be found in all of the resting stages of the spermatocytes (Fig. 14), 
lying usually near the centrosome (Fig. 15). It has the same appear- 
ance as in the earlier stages. 
Soon after the primary spermatocyte has reached its maximum size, 
there begins a gradual condensation of the nuclear contents which can 
readily be followed from its beginning, shown in Fig. 16, to the stage 
shown in Fig. 22 where the entire contents of the nucleus forms a 
rounded mass in which it is not possible to make out any details of 
structure or to determine any of the changes that are taking place. 
McClung (33) has suggested that the term “synizesis” be applied to 
the “unilateral or central contraction of the chromatin in the nucleus 
during the prophase of the first spermatocyte.” I shall, therefore, use 
this term with reference to the stage shown in Fig 22, in order to avoid 
the confusion that has resulted from the misuse of the word “ synapsis.” 
The first evidence of the beginning of synizesis is the appearance, 
near the centre of the nucleus, of a deeply staining mass of tangled 
chromatin threads from which long loops of the spireme go out in all 
directions (Fig. 16). Ata slightly later stage (Fig. 17), this central 
mass appears much larger and there are correspondingly fewer loops of 
the original spireme to be seen. During these early stages in the pro- 
cess of condensation there is frequently found an apparent pairing of the 
chromatin loops as shown in Figs. 18 and 19; but, as in the growth 
stages of the spermatocytes, this pairing of the chromatin loops is by 
no means a constant phenomenon and I cannot but regard it as purely 
accidental. At the stage of Fig. 20, the greater part of the contents of 
the nucleus has become condensed into an apparently homogeneous mass 
from which only a few short filaments of chromatin project. These 
filaments are very much finer than those of the original spireme and most 
of them lie parallel with their free ends invariably pointed to that part 
of the cell in which the centrosome lies. Such a condition of the 
nucleus as that shown in Fig. 20, is met with so frequently that it is 
evidently a well defined stage in which there is a definite orientation of 
the nuclear contents. The gradual condensation of the contents of the 
