556 



PISCES FISHES. 



rakers attached to the branchial arches and serving as 

 strainers; they prevent the food from being swept out 

 with the respiratory current. The gullet leads into a 

 curved stomach ; at the junction of stomach and duodenum 

 numerous tubular pyloric caeca are given off; into the duo- 

 denum opens the bile-duct from the gall-bladder and liver ; 

 the coiled intestine passes gradually into the rectum, which 

 has an aperture apart from those of the genital and urinary 

 ducts. There is no spiral valve, and 

 there are no abdominal pores. A 

 pancreas is absent ; perhaps the py- 

 loric caeca take its place. (In some 

 Teleosteans the pancreas, apparently 

 absent, is combined with the liver.) 

 The peritoneum is darkly pigmented. 

 Respiratory system. Water that 

 passes in by the mouth may pass 

 out by the gill-clefts ; the branchial 

 chamber is also washed by water 

 which passes both in and out under 

 the operculum. The gill-filaments 

 borne on the four anterior branchial 

 arches are long triangular processes, 

 whose free ends form a double row. 

 As there are no partitions between 

 the five gill-clefts, the filaments pro- 

 ject freely into the cavity covered by 

 the operculum. On the internal 

 surface of the operculum lies a red 

 patch, the pseudobranch or rudi- 

 mentary hyoidean gill. Inspiration 

 and taking food into the mouth 



OA 



FlG. 297. Section of a 

 Teleostean gill. 



G.F., Gin-filament ; A., artery are associated with the retraction of 

 bToodr^ d) Lm-arch! (pure the hyoid apparatus ; expiration and 



swallowing are associated with the 

 protraction of the hyoid arch. The usual retractor of the 

 lower jaw is absent in Teleosts, and the lowering of the lower 

 jaw comes about automatically in the retraction of the hyoid 

 arch and the raising of the operculum, in short in the 

 inspiratory phase. A large and quaint parasitic copepod 

 Lerncea branchialis is often found with its head deeply 



