ON DEVELOPMENT OF ATYEPHIRA COMPRESSA. 399 
tureless membrane, on the inner side of which is (6) a layer of 
internal epithelial cells. 
The Formation of Eggs: — In the white band already- 
spoken of (figs. 2 and 3, ger.), we find the youngest eggs. They 
appear perfectly clear and transparent, and measure about 
OOl mm. in diameter, with roundish nuclei of about 0.008 
mm., the size of the nuclei of the inner epithelial layer. A 
section of an unripe ovary, whose lobe measures about O’ 14 
mm. in cross diameter (fig. 9), shows us that the ovary is 
surrounded by a single-layered wall. This wall corresponds to 
the external epithelial layer of a ripe ovary. The sac is filled 
with a general mass of nucleated cells embedded in protoplasm, 
which latter shows a fine granulation in prepared specimens. 
The wall of these cells is extremely delicate, but is clearly dis- 
tinguishable in fine preparations. Some of these cells probably 
arrange themselves around the inner side of the ovarian wall as 
the internal epithelial layer, some surround the larger eggs that 
have moved to one side of the ovarian tube and become the 
follicular (?) epithelium (fig. 9,/ e.), while the others grow into 
primordial ova (p. o.). Thus at this stage of the development 
of the ovary there is no marked difference to be observed 
between the cells that grow into eggs and those that become 
the internal epithelial or follicular cells. 
In the section of a larger ovary we find the youngest ova all 
along the external side of the germogen immediately below the 
external epithelial layer. But the interesting stages are repre- 
sented in those sections (figs. 10 and 11), cutting through the 
oviducts, whose internal epithelial cells ( i . e. od.) are seen to 
acquire a more rounded form {p. o.) and pass uninterruptedly 
into small eggs. Mayer (pp) affirms that a genetic relation 
exists between these two elements. Waldeyer in his “Eier- 
stock und Ei” (^ 5 ) mentions a similar case in the ovary of 
Astacus fluviatilis. Of this last animal Professor Huxley 
also says (-f- 2 ) : “ The growth of these cells gives rise to 
papillary elevations which project into the cavity of the ovary 
and eventually become globular bodies attached by short stalks, 
and invested by the structureless membrane as a membrana 
