106 Miscellaneous. 



its digestive tube, and by the same course excretes carbonic acid 

 gas, which is afterwards evacuated by the anus mixed with the un- 

 absorbed nitrogen. There is consequently in these animals, which 

 also respire by means of branchiae like ordinary fishes, a comple- 

 mentary respiration analogous to the pulmonary respiration of the 

 terrestrial Vertebrata, but having its seat in the intestinal canal ; 

 and M. Jobert has ascertained that in the CaUichthys this tube pre- 

 sents in its anatomical structure peculiarities in connexion with this 

 exceptional function. 



In fact, M. Jobert has found, in the sublaminal portion of the 

 intestine of this fish, a multitude of filiform appendages, arranged 

 in tufts on the free surface of the mucous membrane, and composed 

 essentially of blood-vessels. Up to a certain point these tufts are 

 comparable to the respiratory organs discovered by Reaumur in the 

 rectum of certain larvae of insects, and formed by prolongations of 

 the tracheary system. Just as these internal branchise enable the 

 Libdlulop, to live in the water during the first period of their ex- 

 istence, the sanguiferous appendages of the intestinal coat of Cal- 

 lickthi/s serve to maintain an accessory aerial respiration in those 

 aquatic animals. 



In the memoir upon which the Academy has commissioned us to 

 report, M. Jobert makes known the occurrence of a more or less 

 analogous aerial respiration in several other fishes, the habits of 

 which he has had the opportunity of studying in the valley of the 

 Upper Amazon. These animals live in stagnant water, the tem- 

 perature of which often exceeds 40° C. (104° F.) ; but this medium 

 does not suffice to support their respiration, and they are obliged to 

 come frequently to the surface to draw in air from the atmosphere. 

 Sometimes, even, the drought drives them from their ordinary abode, 

 and they are seen making journeys by land, ot greater or less length, 

 in search of more favourable localities ; when thus engaged they 

 crawl along the ground by means of their pectoral fins. Some of 

 these fishes are peculiar species of CalUchthys, and, like the C. asjjer 

 of Rio de Janeiro, they have the faculty of respiring in two modes — 

 respiring the air dissolved in the circumambient water, and which 

 comes in contact with their branchiae, and respiring also the atmo- 

 spheric air which is introduced by deglutition into their digestive 

 tube, traverses that canal throughout its whole length, and, alter- 

 wards escaping by the anus, produces a sort of continual bubbling 

 in the water. M. Jobert had not at his command the necessary 

 means for determining with precision the chemical composition of 

 the gas which is thus evacuated ; but he was able to ascertain that 

 this fluid contains a large proportion of carbonic acid, and that it is 

 less rich in oxygen than atmospheric air. Lastly, on studying ana- 

 tomically the vascular tufts which clothe the walls of the intestine 

 in which the air, in passing, loses oxygen and becomes charged with 

 carbonic acid, M. Jobert ascertained that many of these sangui- 

 ferous appendages originate from adjacent veins, in the same way 

 as the afferent vessels of a lung. 



