274 
Transactions of the 
[Monthly Microbcopioai 
Juunial, May 1, 1869. 
that fluid, but then they are of a totally different nature from the 
sperm-cells; and moreover, when the blood coagulates, which it 
does very soon after it is drawn, all the corpuscles are involved in 
the coagulum, leaving the fluid part quite free. The slightest addi- 
tion^of water to the medium quite alters the appearance of the cells, 
and gives them all the appearance of having a cell-wall and vesicular 
nucleus (Fig. 9 a). If too much water is added, they burst, 
leaving behind only a mass of granules (Fig. 9 h). Liq. potassse 
has a still more considerable effect in the same direction, swelling 
the cells out to a large size, and having the same action on the 
nucleus. 
The addition of dilute acetic acid has just the contrary effect to 
that of water : it seems to coagulate the cell substance, it makes the 
nucleus more apparent ; in some cases the nucleus (Fig. 9 c) is seen 
to be composed of an irregular mass of granules, coarser than those 
of the rest of the cell ; in others the nucleus may be surrounded by 
a well-defined, but irregular dark hue, which separates it sharply 
from the cell contents (Fig. 9d). Again the nucleus may be a 
regular circle with a smaller one in the centre (Fig. 9e), re- 
sembling a nucleolus ; the effect of prolonged maceration in the 
acid is to dissolve the external part of the cell, leaving the nucleus 
portion floating free in the fluid. 
We now come to a series of cells smaller than the last, but 
connected with them by a regular gradation in size ; some look as 
if they were two cells (Fig. 10 a) joined together by an inter- 
mediate substance, the nucleus being outside the cell, and re- 
sembling it in appearance, so that it is difficult to distinguish one 
from the other; others have the external nucleus (Fig. lOh) round 
or square; some, again, have a portion of the body of the cell 
occupied by a mass of vacuoles in addition to the nucleus, or may 
even have the vacuoles without the nucleus; the vacuoles con- 
tinually break into each other, until a vacant space is left in the 
centre, surrounded by a thin layer of cell substance (Fig. 10c). 
In order to understand (Figs. 11a and b) the significance of 
these cells, it will be necessary to consider the effect of water on 
the mature zoosperm: this re-agent, applied in small quantities, 
swells out the tail gradually until it becomes a round vesicle, the 
rays being first pushed upwards, then disappearing entirely, the 
head in the meanwhile taking a circular form, its edges being 
darker than those of the tail, as might be expected from its more 
solid character. If these figures are compared with Fig. 10, great 
resemblance in shape will be seen, the water seeming to make the 
mature zoosperms retrograde, as if the process of development had 
been the squeezing out of the superfluous moisture from the sperm 
cells, the subsequent addition of which to the mature form reverses 
the process, and restores in some degree the original shape. 
