COPEPODA. 



401 



their further growth are connected with a number of suc- 

 cessive moults, and consist principally in an elongation of the 

 body and the appearance of fresh appendages. In the next 

 larval stage (metanauplius, Fig. 262, 

 6), a fourth pair of appendages, the 

 future first maxillae, makes its ap- 

 pearance behind the three original 

 pairs, which develop into the an- 

 tennae and mandibles. In a later 

 stage four fresh pairs of appendages 

 are formed (Fig. 263). Of these the first and 

 second correspond to the second maxillae 

 and maxillipeds, while the third and fourth 

 represent the first rudiments of the an- 

 terior swimming feet. The functional 

 limbs still resemble those of a nauplius, 

 and it is after another moult that the 

 transformation into the first Cyclops-like 

 form occurs. It then resembles the 

 adult animal in the structure of the an- 

 tennae and mouth parts, although the 

 number of the appendages and of the body 

 rings is still incomplete (Fig. 262, c). 

 The last two pairs of appendages already 

 have the form of short biramous swimming 

 feet, and the rudiments of the third and FlG . 263. Metanauplius of 

 fourth pairs of swimming feet have made fn<? n fecond^ 

 their appearance as projections beset with 

 setae.* The body consists in this stage of 

 the oval cephalothorax ; of the second, third 

 and fourth thoracic segments ; and of an 

 elongated terminal portion, which gives 

 rise to the last thoracic segment and to 

 all the abdominal segments by progressive segmentation, 

 already terminates in the caudal fork. 



Many forms of parasitic Copepoda, for example Lernanthropus 

 and Chondracanthus (Fig. 265), do not get beyond this stage of 

 body segmentation, and obtain neither the swimming feet of the 



* Hartog finds that the setae are formed inverted, and that they 

 become everted when a larval skin is shed. 



An anus ; F', F", F"' the 

 three anterior swimming 

 feet (thoracic appen- 

 dages 2-4) ; 6 brain ; / 

 intestine ; M E median 

 eye ; Mn mandibles ; 

 Maf, MX" first and second 

 maxillae ; Mx.p maxilli- 

 ped (first thoracic appen- 

 dage). After Clans. 



It 



Z III 



D D 



