PARENTAL CARE AMONG FRESH- WATER FISHES. 



457 



both inhabit, the Callichthyids having two rows of plates interlock- 

 ing along the lateral line. The Doradines have also the branchial 

 apertures separated below by a wide isthmus and the gill apertures 

 correspondingly narrowed. The true dorsal fin is well developed; 

 the anal fin is short ; the air bladder is free in the abdominal cavity. 



One of the species of this group— the flathead hassar {Doras han- 

 eoekii) — has long been celebrated from the account of John Hancock 

 (1828) as " one of those fishes which possess the singular property of 

 deserting the water, and travelling overland. In those terrestrial ex- 

 cursions large droves of the species are frequently met with during 

 very dry seasons, for it is only at such periods that they are com- 

 pelled to this dangerous march, Avhich exposes them as a prey to so 

 many and such various enemies. When the Avater is leaving the 



Fic. 36. — A characti'i-istic Doras (Doras- lonfjifspiiiis ) . After Steiudachner. 



pools in which they commonl}' reside, the j^arrow " (a species of Ery- 

 tlirhni.s, probably E. unitceniatus) and the roundhead hassar {Hop- 

 /'osternuni Uttorale) " bury themselves in the mud, Avhile all the other 

 fishes perish for want of their natural element or are picked up by 

 rapacious birds, etc. The flathead hassars, on the contrary, simulta- 

 neously quit the place and march overland in search of water, travel- 

 ling for a whole night, as is asserted by the Indians, in search of their 

 object.'" Hancock, by experiments, ascertained that " they will live 

 many hours out of water, even when exposed to the sun's rays." 

 This endurance is promoted by the narrowed gill apertures and the 

 closeness with which the gill covers can be pressed to the sides. They 

 have also, according to Jobert, a development of sanguiferous papilla? 

 to the intestinal canal serving for aerial respiration analogous to that 

 noticed in Callichthyids, but less complete. 

 SM 1905 33 



