400 
CHITOMATSTJ ISHIKAWA. 
propria. These are the ovisacs. In the mass of cells which 
becomes the ovisac, one rapidly increases in size and occupies 
the centre of the ovisac, while the others surround it as a 
peripheral coat. This central cell is the ovum.” If we con- 
ceive a number of such ovisacs to arise in a special part of 
the ovary, and joined with one another in a line longitudinal 
to the ovary, we shall have a case somewhat similar to that of 
Atvephira, from which, however, it differs in the fact that only 
one, out of a number of cells that constitute an ovisac, grows 
to be an ovum. In Atyephira, as we have already seen, all of 
the cells, or the majority of them, no doubt, in the pouch are 
destined to become eggs. It will be observed further, that a 
complete distinction is here made between the cells which con- 
stitute the follicular epithelium, and those which become eggs. 
The youngest eggs (figs. 9, 10, and 11 ,p.o.) have their size 
equal to those of the epithelial cells. They have a very deli- 
cate contour, and their germinal vesicle generally contains one 
or two germinal dots. They are quite transparent until they 
grow to the size of at least *09 mm. in length. In a little 
older eggs, the protoplasm, however, shows a very delicate 
tint of blue, while the germinal vesicle appears of a very faint 
ochre. There is also present in the ovum one or more 
vacuolar spaces (figs. 10, 11, 13 and 14, vac.). They appear in 
the ovum of about - 035 mm., and their number rapidly in- 
creases when the ovum is transferred into the vitellogen. Ed. 
van Beneden has observed beautiful amoeboid movements in 
very young eggs of Isopods, Amphipods, and some Decapods — 
C rang on vulgaris — when they are held in suspension in the 
serum of blood or in aqueous humour. My experiments have 
failed to detect such a phenomenon in the eggs of Atyephira. 
The germinal vesicle is at first uniformly granulated by fine 
granules, provided with one or more germinal dots, which latter 
can only be distinguished from the granules by their larger 
size, and by their being strongly coloured by staining fluids 
(figs. 10, 11, and 12). As it grows in size these granules 
become coarser, and patches of stellate figures (figs. 13 
aud 14) are formed, probably by the union of the granules. 
