ends of the nine-ring tail fibrils
(Fig. 1).
The central
tail fibrils extend on through the distal centriole into
the proximal centriole.
The neckpiece contains the greatest concentration of
mitochondrial granules found in the spermatozoan (Fig. 2)
and, in addition, a septal structure which may be the golgi
remnant
(Figs. 2 and 3).
The tail sheath is a double membranous structure
surrounding the tail fibrils.
cross section
(Figs. 4,
5,
It is spindle-shaped in
and 6)
had been assumed previously.
rather than round as
The sheath is semipermeable
as evidenced by marked swelling with fixation in hypotonic
solution.
Mitochondrial granules are found throughout the length
of the tail between the sheath and the axial filaments
(Fig. 4).
The larger granules are composed of subunits
and are never found with the ring formed by the ring fibrils.
In the tail fibrils evidence of substructure within
each fibril is found in cross sections of the tails
4, 5 and 6).
(Figs.
There is no lateral association between
adjacent fibrils, the diameters of which are not altered
with changes in osmotic pressure.