ARTHROPODA 269 
of uterine processes in which the ova accumulate, and finally 
opens on the posterior thoracic segment, which in the female is 
fused with the first abdominal. Just at the point of opening 
the oviducts receive the ducts of the spermatheca; this is a 
sac lying within the fused segments, and having a special 
pore through which the spermatozoa make their entrance 
(Fig. 159). 
The testis resembles the ovary in form and position; the 
vasa deferentia are rather coiled, and may be divided into 
different sections, they open into two vesiculae seminales, one 
on each side of the sixth thoracic segment, and these open to 
the exterior upon the same segment (Fig. 158). 
One fertilisation suffices for many broods of ova; the eggs 
as they leave the oviduct are surrounded by a cement-substance 
which forms an investment for each egg and keeps them 
together in an oval mass, which the female carries one on each 
side of her abdomen. One of the ovisacs may contain from 
seventy to ninety ova. 
The Calanidae differ from the Cyclopidae in the possession 
of a well-developed heart, which in Calanella is produced into 
a cephalic artery; and in the fact that their antennae are 
biramous. The Notodelphidae which inhabit the branchial 
chamber of Ascidians have their antennae modified for attach- 
ment, and the posterior thoracic segments of the female are 
fused together and form a brood-pouch in which the eggs 
develope. 
(b) ParasirticA.—The parasitic or semi-parasitic Copepods 
have their mouth parts adapted for piercing and sucking ; their 
body is usually incompletely segmented, and the abdomen is 
reduced. The males are often smaller than the females to whom 
they adhere. 
Most of the Parasitica live on fish, hence their common 
name, fish-lice; they may inhabit the gill-chamber, or the 
pharynx, or they may live on the skin, in which the female 
buries half her body, and in some instances, e.g. Penella, they 
even bore into the body and live partly embedded in the tissues. 
Chondracanthus gibbosus, which inhabits in considerable 
numbers the gill-chamber of the Lophius, or fishing-frog, exhibits 
many of the peculiarities of these remarkable epizoa. The 
