A DEGENERATE GLAND. PRINCE. 225 



Fig. i. German carp {Ct/prinus carpio, Linn ). The swim-bladder (s b) con- 

 nected by duct (d) with the oesophagus (ces) and with the ear by a 

 chain of ossicles (i. k. 1.). (Modified from Weber's well-known figure). 



Fig. 5. Ventral s'iew of skull and anterior vertebrae of the loach {Cobitis bar- 

 batidn-s, Linn.), showing osseous bull* which cover the swim-bladder. 

 The bulhe are expansions of the lateral processes of the 2nd. and 3rd. 

 vertebra. 



P/ate 21. 



Fig. 1. Diagram, showing the diverticulum or rudiment of the swim-bladder 

 on the dorsal wall of the oesophagus of an embi-yo fish, viewed from 

 above. 



Fig 2. The same, viewed lateralh'. 



Fig .3. Diagram, showing the bifid diverticulum or rudiment of the lungs on 

 the ventral wall of the oesophagus of a frog. Viewed from below. 

 (Modified from Wiedersheim). 



Fig. 4. Section (trans, vert.) of the oesophagus of an embrj'O haddock (Mtlano- 

 grammus) inside the egg, three days before hatching, showing dorsal 

 diverticulum or swim-bladder (s b.) and ventral diverticulum or 

 liver (1 ) The section was cut in a somewhat oblique vertical p'ane. 



Fig. 5. Section (trans, vert.) of larval haddock, three days after hatching 

 showing more advanced condition of swim-bladder, liver, gallbladder, 

 and covering of flattened mesoderm cells. x 200. 



Fig. 6. Section (trans, vert.) of portion of swim-bladder of gurnard {Trigla 

 gurnardus) 6 mm. long. x 175. 



Fig. 7. Section do. do. of cod {Gadus morrhua) 6 mm. long. 



X 175. 



Fig. 8. Section do. do. of pollack (PoUachius vireiis) 6'5 mm. 



long. X 200. 



Fig 9. Section do. do. of cod, 9 2 mm. long. x 200. 



Fig 10. Section do. do. of gemmous skulpin {CaUionymus lyra) 



7 8 mm. long. x 200. 



Fig. 11. Forepart of larval haddock (from life), 7 days old, showing the swim- 

 bladder (sb.) above the stomach (stom ) and densely covered with 

 black pigment. 



Fig. 12. Section of portion of swim-bladder of gurnard (10 mm. long) showing 

 five distinct layers in the walls. 



Fig. 13. Post-larval eunner {Tautogolabrus adspersus, Wafb. ) showing swim- 

 bladder (s b) in transparent body of the fish. x 8. 



Plate 22. 



Fig. 1. Dissection of stomach, swim-bladder, &c., of the conger (Congtr 

 vulgaris, Cuv.) showing two globular vascular bodies (a. a ) near the 

 opening of thj duct in the swim-bladder (s b. ) 



