ON DEVELOPMENT OF ATYEPHIRA COMPRESSA. 
393 
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The Ovary. 
The female generative organ of Atyephiracompressa 
consists of two elongated sacs joined with each other near the 
anterior end. They extend in the body cavity parallel to, and 
above, the digestive canal, beginning at the middle portion of 
the cephalothorax, a little in front of the heart, and reaching 
posteriorly as far as the middle of the second abdominal 
segment. At about the middle point of its length each of 
these sacs sends out a canal laterally, which taking a direct 
course downwards, opens on the internal face of the basal 
joint of the third thoracic leg. The mouth of this canal is 
covered over by a membrane which is slightly raised above the 
level of the general surface. There is a transverse slit across 
the middle of this membrane, which thus forms a sort of a 
valve, and prevents water from getting into the ovary (fig. 1, 
o.oc?.). The elongated sacs above mentioned constitute the 
essential part of the ovary, while the two lateral ducts serve as 
oviducts. 
The fully ripened ovary (fig. 2) measures about 4.5 — 6 mm. 
in length and 4 mm. in breadth across the point of junction. 
These measurements, however, vary according to the size of the 
animal, for an animal not larger than 10 mm. in length is 
often provided with a small ripe ovary, containing a small 
number of eggs. 
On the under side of each ovarian tube there is to be seen 
a narrow transparent band, sharply distinguished from the dark 
green colour of the ripe ova (fig. 2, ger.), running the whole 
length of the ovary. Anteriorly it runs nearer to the median 
than to the outer side. It meets with its fellow of the opposite 
side at the point of junction, whence it takes its course diagon- 
ally outwards to the region of the oviduct in a curved line ; here 
it turns posteriorly, and taking its course along the outer edge 
of the ovarian tube, ends blindly at its hind extremity. These 
bands are very well seen when the ovary is acted on by acids 
