PARENTAL CARE AMONG FRESH-WATER FISHES. 



463 



the pectorals are low and horizontal and also spiniferous. From 

 tropical American streams about 30 species have been obtained. 



The typical Callichthyids of the genera Callichthys and Hoploster- 

 num are most at home in streams with a muddy bottom and in the 

 shallow ditches and pools of marshes. In such places they may con- 

 gregate in considerable numbers, and when the Avater is low may be 

 readily caught with dippers or pails and even with the hand. When 

 so disturbed they are apt to express their feelings by rumbling or 

 grunting sounds. At all times they may come to the surface of the 

 water from time to time to take in' gulps of atmospheric air, and 

 these emergences become more frequent with the lowering of the 

 water. At length, if the water entirely disappears, the resort to 

 atmospheric air supplants aquatic respiration, and a curious comple- 

 mentary mode of respiration is substituted for the normal branchial 

 method. This was discovered by a French physiologist — Professor 

 Jobert — who visited Brazil in 1877 and 1878 and undertook some in- 



FiG. 38. — IlopJostcrniim litturale. After Boulenger. 



vestigations at the instance of the Emperor. These were favorably 

 reported on by a special committee of the French Academy of 

 Sciences of which Milne EdAvards was the mouthpiece. 



Like the common loach of Europe, according to the reporter, the 

 ty2:)ical Callichthvid '' frequently swallows bubbles of air, parth^ ab- 

 sorbs the oxygen from them by the walls of its digestive tube, and by the 

 same course excretes carbonic-acid gas, which is afterwards evacuated 

 by the anus mixed with the unabsorbed nitrogen." There is, in fact, 

 " a complementary resjuration analogous to the pulmonary respira- 

 tion of the terrestrial vertebrates, but having its seat in the intestinal 

 canal." Jobert also "ascertained that in the CaUiclitJn/x this tube 

 presents in its anatomical structure peculiarities in connection with 

 this excejitional function." In '* the sul)Uiminal })ortion of the in- 

 testine " are developed a '' nudtitude of filiform appendages arranged 

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

 essentially of l)lood vessels." It is these " sanguiferous appendages 

 of the intestinal coat of C'allicltt/ii/s " that '* serve to maintain an ac- 



