278 J. B. GATENBY AND J. H. WOODGER 
with the nucleus at one spot. A change has come over the 
proacrosomic structures: these have finally fused to form 
a single large bead, the proacrosome, within its vacuole (v), 
and around the entire periphery of the inner granule an outer 
rind has been secreted (:za). These two regions are known 
as the outer and inner region of the proacrosome (hitherto 
proacrosomic granules). The proacrosomic apparatus moves 
through the archoplasm and finally becomes stuck upon the 
surface of the nuclear membrane, towards the front end of the 
nucleus, and hereafter may be called the acrosome (PI. 12, 
fig. 10). On the side of the acrosome which touches the nuclear 
membrane the outer region of the acrosome is completely 
pushed away, so that the imner region of the acrosome alone 
touches the nuclear membrane in the mid-region of the 
acrosome ; at the edges, however, as shown in PI. 12, fig. 11, 
the outer region of the acrosome les in contact with the 
nuclear membrane. 
The Golgi apparatus (i.e. all the dictyosomes), and the 
archoplasm upon which it lies, keeps its position, partly embrac- 
ing both the acrosome and one side of the nucleus (as shown 
in Pl. 12, figs. 10 and 11) some considerable time, during which 
the two parts of the acrosome grow rapidly. Eventually, 
however, the apparatus and the archoplasm break away as 
shown in Pl. 12, fig. 12, and begin to drift back towards the tail 
end of the spermatid (Pl. 12, fig. 13). 
The inner region of the acrosome gradually becomes flattened 
out on the front of the spermatid nucleus, and the whole 
structure undergoes the changes shown in Pl. 12, figs. 12-15. 
9 On the Subsequent Behaviour of the Golgi 
Apparatus and Archoplasm. 
By the stage drawn in Pl. 12, fig. 12, the Golgi elements and 
archoplasm have begun to drift down the elongating sperm 
cell, and in PI. 12, fig. 18, this apparatus has completely flowed 
away from the nucleus. Between the stages depicted in Pl. 12, 
figs. 18 and 14, the definitive middle-piece Golgi apparatus 
appears as described by us on p. 269. 
Between the stages in Pl. 12, figs. 15 and 16, the apparatus 
