220 
W. A. JIASWEM.. 
processes (ducts) in the neiglibourhood of the posterior part 
of it. They do not contain any yolk-granules as sucli, 
and the latter must be formed within tlie growing ovum itself, 
the secretion providing the requisite material. That they do 
perform this function I conclude from their situation, and 
from the fact that they are the only organs of sufficient bulk to 
be capable of producing with rapidity the relatively con- 
siderable mass of substance which the ovum has to receive 
before it reaches maturity. 
In mature females there is nearly always a single ovum 
(figs. 1-6, and 10, 11, or. ^), which is vei'y much larger than 
the second in size, and which causes the distension of the 
legion of the body in which it lies and the compression of 
the other organs — intestine, nerve-cord, and muscular S 3 ^stem. 
The cavity in which it lies, a part of the coelom, is situated 
between the cirri of the third pair. A pair of forward 
extensions of this cavity enclose the rest of the ovary in the 
shape of right and left lobes. The entii’e ovai-y is enclosed 
in a thin layer of splanchnic coelenchyme, which is produced 
inwards in such a way as to form an investment for each of 
the fully formed ova. Each ovarian lobe contains a. single 
row of ova, diminishing in size from behind forwards. 'This 
row bends inwards at the apex of the lobe, and turns back 
on the inner side to become merged in a nucleated layer 
which is not separable from the ccelenchymic investment, 
and in which occasional mitotic figures are to be detected. 
The principal ovum is loaded with large spherical yolk- 
granules, and in some cases the ovum next in size contains 
more or fewer of these bodies; in the rest yolk-granules are 
absent. In sections which have been well stained with 
hgematoxylin the outermost layer of the largest ovum, and 
usually that of the next in size, is darkly coloured by the dye, 
and appears as an investment of a vacuolated character 
sending numerous short processes inwards. This is obviously 
not a special investment, but a superficial protoplasmic 
la^mr having an affinity for a nuclear stain that in all other 
parts affects in the same degree only the nuclei. 
