228 



THE LIFE OF CRUSTACEA 



time in this condition, the larva again acquires the 

 power of swimming, and leaves its host. Both sexes 

 become mature in this free-swimming stage (Fig. 73, 

 C, D), and impregnation is effected. The males 

 die without developing further, but the females seek 

 a second host, a fish of the family Gadidae, such as 

 the Cod, Haddock, etc., and, settling on the gills, 

 become metamorphosed (Fig. 73, E) into the adult 

 form described above. 



Within the gill cavities of the strange-looking fish 

 known as the Angler or Fishing-frog (Lophius 

 piscatorim) there may often be found specimens of 

 another parasitic Copepod, Chondr acanthus gibbosus. 

 It has a soft, unsegmented body about half an inch 

 long, provided with numerous blunt lobes which 

 give it a very irregular shape. On the under-side, 

 near the front, are forked lobes representing two 

 pairs of the swimming feet. At the hinder end are 

 usually attached a pair of long thread-like egg-masses. 

 Just at the point where the egg-masses are attached, 

 close inspection of the under-side of the body will 

 reveal a very minute maggot-like object. This is 

 a male individual, which is attached, like a secondary 

 parasite, to the body of the enormously larger female. 



In all the cases mentioned, the animal is parasitic 

 in the final state of its existence at least in the 

 female sex but there are a few Copepoda which are 

 free-swimming, both when young and when adult, 

 but parasitic in the intermediate stages. Among the 



