CHAP TER TEE 
CRUSTACEA (CONTINUED): COPEPODA 
Order II. Copepoda. 
THE Copepods are small Crustacea, composed typically of about 
sixteen segments, in which the biramous type of limb pre- 
dominates. They are devoid of a carapace. Development 
proceeds gradually by the addition posteriorly of segments to a 
Nauplius larval form. Paired compound eyes are absent, except 
in Branchiura, the adult retaining the simple eye of the 
Nauplhus. 
In a typical Copepod, such as Calanus hyperboreus (Fig. 25), 
we can distinguish the following segments with their appen- 
dages: a cephalothorax, carrying a pair of uniramous first an- 
tennae (7%! Ant.); a pair of biramous second antennae (2"7 Ant.) ; 
mandibles (Md.) with biting gnathobases and a palp, and a pair 
of .foliaceous first maxillae (Jf.'). Two pairs of appendages 
follow, which were looked upon as the two branches of the 
second maxillae, but it is now certain that they represent 
two pairs of appendages, which may be called second maxillae 
(Mz."), and maxillipedes (M/ap.) respectively. Behind these-are 
five pairs of biramous swimming feet, the first pair (7h.’) 
attached to the cephalothorax, the succeeding four pairs to four 
distinct thoracic somites. Behind the thorax is a clearly 
delimited abdomen composed of five segments, the first of which 
(Abd.") carries the genital opening, and the last a caudal furea. 
The Copepods exhibit a great variety of structure, and 
their classification is attended with great difficulties. Claus? 
based his attempt at a natural classification on the character of 
1 Grundziige der Zoologie, 4. Aufl. 1880, p. 543. 
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