Fig. 87. — Two dissections showing the gills of the Fresh-water Crayfish. 



In A the right gill-cover has been removed, but the gills are undis- 

 turbed : in B the podobranchise {pdb. in a) are cut away, and the outer 

 set of arthrobranchice {ay-b^) turned down to show the inner arthro- 

 branchiDe {arb) and the pleurobranchiai (//. b). 



All the gills are numbered according to the segment from which they 

 spring, the first thoracic segment being numbered 6, the last 13. 



ep. 5, scaphognathite. 



ab. I, ab. 2, abdominal segments ; c^, antennule ; a^, antenna ; 6-8, 

 maxillipeds ; 9-1.^, legs ; pi. i, first pleopod. 



(From Lang, after Huxley.) 



