r7>i^, arh.') /*H».12 'irln j>il>\:i 



am 



Fig. 4. — Astacus Jluviaiilis.~-lT\ A, the gills, exposed by the removal of the "branchio- 

 stegite, are seen in their natural position ; inB, the podobranchia;.(5ee p. 75) are re- 

 moved, and the anterior set of ai-throbranchiae turned downwards ( x 2) : i, eye-stalk ; 

 3, antennnle ; 3, antenna ; ^, mandible ; 6, scaphoghathlte ; 7, first maxillipede, in B 

 the epipodite, to which the line points, is partly removed ; 8, second maxillipede ; 

 9, third maxillipede ; 10, forceps ; lA, fourth ambulatory leg ; 15, first abdominal 

 apfiendage ; xv., first, and xvi., second abdominal somite; arh. 8, arb. 9, arh. IS, 

 the posterior arthrobranchiae of the second and third maxillipedes and of the third 

 ambulatory leg ; arb'. 9, arb'. IS, the anterior arthrobranchiae of the third maxillipede 

 and of the third ambulatory leg ; pbd. 8, podobranchia? of the second maxillii)ede ; 

 pbd. 13, that of the third ambulatory leg ; plb. IS, pW. 13, the two rudimentary 

 pleurobranchiaj ; plb, H, the functional pleurobranchia ; r, rostrum. 



