46 
H. E. Jordan 
remain connected end-to-end by delicate linin threads. At this stage 
the chromosomes — with the exception of the accessory — again stain 
faintly and appear coarser bnt less compact, and show an indication of 
a median split (figs. 20 and 21). It may be well to emphasize here that 
throughout synapsis and subsequently, the accessory chromosome retains 
its intense staining quality, its sliarp contour (though it varies somewhat 
in size, sometimes appearing distinctly bipartite — occasionally appearances 
indicate even complete Separation of two elements) and its characteristic 
Position next the centrosphere. Moreover, it is frequently attached to 
one of the chromatic threads 3 ). 
But tliere are numerous cells of the stage of development illustrated 
in fig. 21 which contain still other non-reticular elements whose signifi- 
cance is uncertain. Besides the chromatin nucleolus (always at the idio- 
zome pole of the nucleus) and the plasmosome (which has an apparentlv 
random position in the nucleus) tliere frecpiently appear one or several 
larger or smaller metachromatic masses. These frequently appear in 
process of fragmentation. They are tentatively interpreted as the earlier 
nuclear forerunners of the mitochondria. 
e) Centrosphere (idiozome). 
I have spoken of a “centrosphere” because in the material stained 
with iron-haematoxylin I am unable, except in rare instances (figs. 13 
and 15), to demonstrate a distinct central granule with in the homogeneous 
arehoplasmic mass (attraction sphere; idiozome) which conforms to a 
centrosome. This may be due simply to its small size relative to the 
large sphere. However, in seetions stained with Delafield’s haema- 
toxvlin the pale sphere contains numerous dark granulös. It is possible 
that one or several of these correspond to the centrosome of other 
forms. The centrosphere is conspicuouslv present at all stages from the 
festing primary spermatocyte (fig. 10) to the spermatid (fig. 59). Its later 
history will be considered in connection with the description of sperm- 
formation. 
In the resting stages the centrosphere has a short oval form closely 
applied to the nuclear membrane (figs. 9, 10 and 11). Düring synapsis 
it becomes more elongated and conforms to the eurvature of the spherical 
nucleus (figs. 13 to 17). In early prophase it draws away from the wall 
slightly and divides into two spheric or oval bodies (figs. 22 to 26). The 
maturation spindles (figs. 34 to 37) end in points marked apparently by 
a chromatic granule unaccompanied by a distinct sphere. It would seem 
