CHAPTER III 



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 

 Nauplius. 



In a typical Copepod, such as C'alanus hyperhoreus (Fig. 25), 

 we can distinguish the following segments with their appen- 

 dages : a cephalothorax, carrying a pair of uniramous first an- 

 tennae (l^^Ant.) ; a pair of biramous second antennae (£''"^Ant.) ; 

 mandibles {Md.) with biting gnathobases and a palp, and a pair 

 of foliaceous first maxillae {AIx}). 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 

 {Mx?), and maxillipedes (Mxp.) respectively. Behind these are 

 five pairs of biramous swimming feet, the first pair {Th}) 

 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 furca. 



The Copepods exhibit a great variety of structure, and 

 their classification is attended with great difficulties. Clans ^ 

 based his attempt at a natural classification on the character of 



' Orundziige der Zoologie, i. Aufl. 1880, p. ,543. 

 55 



