BRANCHIURA. 



245 



limbs, and these again are followed by an unsegmented abdomen 

 with terminal fnrcal appendages (in the young form). In the adult, 

 these latter have shifted dorsally. The young are further distinguished 

 from the adult by the small extent of the cephalo-thoracic shield 

 (Fig. 116), which does not yet cover the thoracic segments dorsally. 

 The further metamorphosis principally concerns the transformation 



116.— Newly-hatched larva of Argulus foliaccus (after Claus). a', first antenna; o", 

 second antenna ; md, mandible ; mdt, mandibular palp ; mf, first, mf", second maxilli- 

 pede ; p 1 , p*, first four swimming limbs. 



the different limbs. In the newly-hatched larva, the first antenna 

 [a') is short, three-jointed, with a large hook-like appendage on its 

 basal segment. The second antenna (a) is distinctly larger and 

 biramose, an endopodite ending in a hook, and an exopodite provided 

 with setae being distinguishable in it. In the mandible (md) are 

 found a basal segment (masticatory blade), which becomes included 



