THE TELEOSTEI. 163 



(e.g., Lophius, Diodon). In MaJthcea tlie number is reduced 

 to five, only the anterior series of the third arch being 

 developed ; and in AmpMpnmis cuchia only the second bran- 

 chial arch possesses branchial filaments, the first, third, 

 and foiu-th being devoid of them. 



Many Teleostean fishes possess accessory respiratory 

 organs. These may take the form of arborescent appendages 

 to the upper ends of some of tne branchial arches, as in 

 Clarias, Heterobranchus, and Heterotis ; or, as in the Climb- 

 ing Perch {Anabas) and its allies, the epipharyngeal bones 

 may enlarge and acquire a labyrinthic honeycombed 

 structure, and support a large surface of vascular mucous 

 membrane ; or, as in the Ckipeoid {Liitodeira chanos), an 

 accessory gill may be developed in a curved csecal prolonga- 

 tion of the branchial cavity. Finally, in Saccobranclms 

 singio and in Amphipnous cuchia, the membrane lining the 

 branchial chamber is prolonged into sacs, which lie at the 

 sides of the body, and receive the blood from the divisions 

 of the cardiac aorta which supply the branchiae, while they 

 return it into the dorsal aorta. 



All these fishes (except liidodeira) are remarkable for 

 their power of sustaining life out of the water. Many in- 

 habit the marshes of hot countries, which become more or 

 less desiccated in the dry season. 



The kidneys of Teleostean fishes i-eceive a great part of 

 their blood from the caudal vein, which ramifies in them. 

 They vary greatly in length, sometimes extending along 

 the whole under-surface of the vertebral column, from the 

 head to the termination of the abdomen. The ureters pass 

 into an urinary bladder which opens behind the rectum. 



The brain in the Teleostei has solid cerebral hemispheres, 

 and. when viewed from above, the thalamencephalon is 

 hidden by the approximation to the hemispheres of the large 

 and hoUow optic lobes of the mesencephalon, which has a 

 pair of inferior enlargements, loM inferiores. There is a 

 peculiarity about the structure of the optic lobes, which has 

 "■iven rise to much diversity of interpretation of the parts 



