ON THE DEVELOPMENT OF THE SPERMATOZOA. 
85 
going primary division. The sign of this division is a cleft on 
both sides of the spermatosphere, not running transversely, but 
generally diagonally. The cleft on one side is, moreover, deeper 
than on the other. Sperm-polyplasts of this kind are found in 
varying states of division till two new polyplasts result, each 
consisting of eight or more spermatoblasts, which continue to 
go on growing (fig. 29). 
I am doubtful as to whether all the sperm-polyplasts divide 
when they reach this state, or whether some do not continue their 
development without a break. I am inclined to think that this 
is the case, as the final form, from whence the sperm rods arise, 
has two shapes — either a spherical or an oval. The first would 
result where the corpuscle had undergone division at this 
stage ; the second, where there had been no multiplication of 
the kind. 
After this division the peripheral spermatoblasts continue to 
multiply by fission in planes radial to the whole polyplast. The 
whole corpuscle increases slightly in size, and the central mass 
of protoplasm or blastophor begins to attain some magnitude 
(figs. 30 — 36). Henceforward it can be distinguished as a 
large central corpuscle. 
When the spermatoblasts have reached a suitable size, 
the coat of protoplasm which has been enveloping the nucleus 
begins, in each, to collect in a small cap or knob-like mass at 
the distal end (fig. 37), and, from its high refractive power, con- 
stitutes a very conspicuous part of the spermatoblast, even in the 
fresh state. From this knob proceeds a small whip-like fila- 
ment of protoplasm, at first very fine and short. It soon grows 
out into a lash, and constitutes the vibratile tail of the mature 
spermatozoon (figs. 38 — 42). 
It does not stain readily, and requires, at all times, a good 
light to be seen distinctly in its early stages. 
The spermatoblast at this stage may be described as pear- 
shaped, with the stalk of the pear turned outwards, and consti- 
tuted by the whip-like filament, the body of the pear by the 
nucleus which joins the blastophoral corpuscle by another thin 
process of unstained matter. 
The sperm-polyplast now is spherical or oval in shape, con- 
sisting of a number of elongated spermatoblasts, varying in 
amount according to the size of the sphere, supported like pins 
on a pincushion on the central blastophor, which has swollen up 
considerably, and can be seen in optical section, or even better 
where rough usage has rubbed some of the spermatoblasts off 
or flattened out the whole polyplast. 
When the polyplast has reached this stage all further multi- 
plication of the spermatoblasts ceases, and tlieir further dc- 
