Miscellaneous. 107 



Other fishes of the Upper Amazon belonging to the genua Doras, 

 and living in the same waters, resemble the species of Callichthys 

 in their mode of aerial respiration, as well as in the structure of 

 the raucous coat of the intestine in which this function is performed; 

 and M. Jobert has ascertained that nearly the same thin" takes 

 place in the fishes known as Hi/postomi. These animals also inces- 

 santly swallow air, and their intestine, into which the air is thus 

 introduced, is almost equally rich in blood-vessels ; but the air 

 which has served for the intestinal respiration of the Hi/postomi is 

 not evacuated by the anus, and returns towards the mouth, to be 

 expelled either by that orifice or by the branchial apertures. The 

 complementary respiratory apparatus thus formed appears to be less 

 perfect than in CaUichthi/s : and, moreover, M. Jobert has ascer- 

 tained that the Hypostomi are incapable of living so long out of the 

 water as these latter fishes; they die within from five to seven 

 hours. 



M. Jobert has further ascertained the existence of a complemental 

 aerial respiration in Suclis gigas and in certain Enjthrini of the 

 Upper Amazon ; but in these fishes it is no longer the intestine that 

 plays the part of lungs, but the so-called swimming-bladder is 

 the seat of this function. Ichthyologists know that in the Ery- 

 ihrini this pneumatic sac, which communicates with the outer world 

 by means of the oesophagus, is furnished internally with little 

 alveolar chambers ; but the walls of these cells, which had been 

 studied only in animals preserved in spirits, were regarded as simple 

 membranous folds, and in consequence most physiologists denied 

 them the characteristic structure of a lung. M. Jobert has removed 

 all uncertainty upon this point ; he has ascertained that in these 

 Erythrini there is really an aerial respiration which gives these 

 fishes the power of living for a long time out of water, that these 

 animals regularly renew the air contained in their i^neumatic bladder, 

 and that the walls of this organ are richly provided with blood- 

 vessels, most of which originate from the venous system. Lastly, 

 M. Jobert has ascertained experimentally that, by obstructing the 

 canal by which this organ communicates with the atmosphere, the 

 asphyxia and death of the fishes just mentioned are produced. 



But all the fishes designated by zoologists by the generic name 

 Erythrinus do not enjoy the faculty of living in this way out of tho 

 water. M. Jobert has found that the Erythrinus trarhina of the 

 Amazon is in this case ; and this exception seems to corroborate the 

 conclusions of the author as to the functions of the so-called swim- 

 ming-bladder in the other Erythrini ; for in the fish just mentioned, 

 M. Jobert has ascertained that the cells and the venous network, so 

 highly developed in Erythrinus tceniatus and E. brasilicnsis, are want- 

 ing, and that the walls of the pneumatic sac are smooth. 



We see therefore that the journey of M. Jobert in the valley of 

 the Upper Amazon has already furnished physiological zoology 

 with very interesting facts, which establish new bonds between the 

 ordinary fishes, the Lepidosirens, and the perennibranchiate Ba- 



