J. Johnstone 
403 
at the periphery, but much more compact in the region of the median 
bridge. 
The ova (PI. XXII, fig. 14) are polyhedral in shape towards the 
periphery of the ovary, but are quite spherical in the median parts. 
Their average diameter is about O'Ol mm. There is no distinct cell 
membrane. The nucleus has a very distinct membrane ; the linin sub¬ 
stance stains very faintly; and the chromatin is present as a synapse which 
exhibits a radiating arrangement of the threads. The nucleolus is very 
prominent and sometimes contains a round faintly staining body, some¬ 
times one or two strongly refringent granules. In the cell substance, at 
the opposite pole of the egg to that towards which the nucleolu,® is situated, 
there is a “ Nebenkern ” in the form of a small round lightly staining 
body just outside the nuclear membrane. I have seen no signs of dividing 
cells in the ovary; probably this division occurs at a very early stage. 
The oviduct. This takes origin at the posterior side of the 
median bridge, and here is situated the peculiar structiu’e called the 
“ Schluckapparat ” by Pintner (1889), and the “Sphincter ovaricus” by 
Monticelli. It is a modification of the membranous wall of the ovary, 
which here becomes greatly thickened, and encloses a lumen which is 
about twice the diameter of a single ovum. Outside this there are 
a number of fibres arranged to form a thick ring, and running for the 
most part circularly, though some of them are also radial and run out 
into the surrounding tissues. These fibres have been described as 
muscular, though I suspect, from their reaction towards methyl-blue- 
eosin, that they are rather of the nature of elastic tissue. The whole 
structure only occupies some half dozen thin sections and then the 
diameter of the oviduct contracts till it is too narrow to admit of the 
passage of a single ovum. The “ Schluckapparat ” is described as able 
to execute rhythmic movements, expanding to allow an ovum to pass 
out from the ovary, and then contracting so as to force it into the 
oviduct. I suspect, however, that it is only an elastic sphincter, and 
that the expulsion of the eggs from the ovary may be brought about by 
the contraction of the muscles of the proglottis. 
The oviduct enlarges considerably in calibre beyond the “ Schluck¬ 
apparat.” Its wall here consists of an inner single layer of rounded 
cells rather flattened against each other in the manner of a true 
epithelium ; of a basement membrane ; and of an outer rather in-egular 
layer of cells with very indistinct cell bodies. Further away from the 
ovary this outer layer of cells breaks down still more so that we have 
rather isolated nuclei embedded in a cell debris. The inner layer of cells 
