CE USTA CE A— GILLS 



327 



In the Isopoda the delicate-skinned lamellEe of the pleopoda serve 

 for respiration, either both the lamellse of a foot or only the inner, the 

 outer one being hard-skinned and serving as a covering plate to protect 

 the inner one. 



The gills of the Stomatopoda (Squilla) are found as branched 



att'ii o-i-K tttSj 



Fig. 228.— a and B, Gills of Astaous fluTlatiUs. In A the branchiostegite is removed. The gills 

 are seen in their natural position. In B the podobranchiEe are cut off, and the outer arthrobranchiaB 

 turned back downwards. Twice the natural size, aj, 03, 1st and 2d antennas ; 3, mandible ; ep^, 

 epipodite of the 2d maxilla ; 6, 1st maxillipede ; 7, 2d maxiUipede ; S, 3d maxillipede ; 9, forceps 

 (cut-ofi) ; 10-13, the 4 succeeding ambulatory feet ; plj, 1st pleopod ; afej, a&g 1st and 2d abdominal 

 segments ; pdb, podobranchiaj ; arb, inner, arfei, outer arthrobranchiaj ; plb, pleurobranchi^ ; the 

 numbers attached show the appendages to which the gills belong, in order from before backward, 

 beginning with the anterior antenna as No. 1 ; gh, articular membrane between the body and basal 

 joint of the protopodite (after Huxley). 



appendages on the outer lamellse of the abdominal swimming feet 

 (pleopoda). The arrangement of the gills in Siriella (Mysidce) 

 is similar ; they here also occur in the males as appendages of the 

 pleopoda, but on their inner branches. 



The gills of the AmpMpoda, ScUzopoda (except the Mysidce), and 



