418 
W. A. HA SWELL. 
alcohol and ether, followed by a per cent, solution of the 
same. The celloidin blocks, hardened in chloroform, are 
then finally embedded in the hardest paraffin in the usual 
way. The staining agents employed almost exclusively were 
Ehrlich’s liaBinatoxylin, or Mayer’s hmmocalcium, followed by 
eosin. 
III. Formation of the Egg. 
The ovary (germarium) in Temnocephala fasciata, 
and in all the Australasian species of the genus (PI. 23, fig. 1), 
is a solid ellipsoidal mass of ova enclosed in a thin capsule of 
muscular fibres. At the right extremity, which is the one 
situated nearest to the oviduct, is the largest ovum, which is 
more rounded in form than the rest. The remainder decrease 
gradually in size towards the left, the largest of them ex- 
tending across the entire width of the ovary. At the left 
end is a mass of smaller ova, which show evidence of slow 
multiplication by mitotic division. The full-grown ovum, at 
the right-hand end of the ovary, is about O’ll mm. in long 
diameter. Its protoplasm is densely loaded with very fine 
granules, and contains, in addition, a number of much larger 
rounded masses of very definite spherical form. The nucleus 
is large, about one third of the diameter of the ovum itself, 
with spherical nucleolus, and a fine, open, achromatin net- 
work . 
The ripe ovum becomes detached from the others, and 
passes into the oviduct, which opens through the capsule of 
the ovai’y. It must then pass along the oviduct to the 
ootype, where it becomes surrounded by a mass of yolk-cells 
and the whole then becomes enclosed in a chitinous shell, 
the substance of which is secreted by the shell glands. 
Considerable differences in detail distinguish the various 
species of Temnocephala as regards not only the male 
parts oE the reproductive apparatus, but also the female. 
But in all the species which I have had the opportunity of 
examining, the essential features of the parts concerned in 
