respiratory pouches 



A ACIPEN5ER 

 bladders ossocioted with inner ears 



C CLUPEA HARENGU5 



CYPRINOID 



uct to exterior 



B LEPISOSTEUS AND AMIA 



tunica externa 



H 



CATOSTOMUS 



anterior gas-secreting chamber 



rete mlrablle 



-X 



posterior chamber 



anterior cardinal vein 



esophagus 



_ ^^■^'■''' duct of Cuvier. 



ductus pneumcticus 



hepatic vein 



coeliaco-mesenteric arte 



dorsal aorta 



posterior cardinal vein 



esophagus 



I PHYSOCLIST WITH POSTERIOR CHAMBER 



■^rete mirabile 

 portal vein intestinal artery 



J PHYSOCLIST WITH OVAL 



vestigial pneumotic duct 



Figure 9-32. Variations in the structure and relationships of the swim bladder. F-H, three stages in development of the sw,m bladder of Catastomus. 

 (C after Tracy, 1920; D, E, I, J after Goodrich, 1930; F-H after Nelson, 1959) 



In the evolution of the BrachiopterygH. the bHateral pha- Ofher gno.hos^ome fishes Miklucho-Maclay 0867) found 



ryngeal pouches joined ventrally in a fashion parallel to that a rudimentary dorsa d.vert.culu.. from ,h esoph^S^s m 



observe? in the choanate. That parallelism is involved is embryos of GaUus, MusUlus (^'S"-, ^'^^ C), and 5,« /^^ 



suggested by the originally paired glotti, the muscular These rudiments were ""^ /^^^^''^ , "^^^^^^f,^*^^ " '" 



nature of the sac wall and the lack of alveolar sacculations workers, although Mayer (1894) found one tn the adult of 



in Pol bterus Mustetus laevm. Pits in the esophageal wall are observed in 



THE RESPIRATORY SYSTEM • 285 



