( 21 ) 



XLT. In the order Pi.ectognatiit, several of {\\c, 

 ,„ , ,,. i'iimWy Oymiiodoutes iivo. t'oandaaecnd- 



riectognaUii. . ■ n t ^ 



iiig rivers tor some clistauee, espe- 

 cially species of the gcmis Tetrodon, but they do not apjjcar 

 to he considered fit for food anywhere (except some sea 

 species amongst the Andamanese). Still in Burma, a closely 

 allied fish, XenopterusiKvitus, is extensively taken in the lower 

 provinces, and esteemed as food l)y the people of the country. 

 XLII. In the Suh-Class Ouonduoi'teuvgii, order 



Plagiostomata, there are sohk; 

 CaiiiiMginous fisiiea. spccics wliicli asccud rivcrs for preda- 



ceous purposes, but are not esteemed 

 as food. Amongst the family of sharks, the C(trcha)^ias Gaiigc- 

 tioiis ascends rivers, but not very often far l)eyoud tidal inllu- 

 eucc; however, I have seen it at Cuttack, and in the Pegu river : 

 whilst a species of saw-fish, Prlsiis, is likewise found to pro- 

 ceed as high; neither breed in the rivers. Amongst the Tri/go- 

 nidce, the T. ttarnak is also frequently found above tidal 

 influence. 



Respiration of Indian Pishes. 



XLIII. Before commencing the subject of the sudden 



appearance of fishes in Indian tanks 



Respiration of fi.iica : water- j^ftev falls of rain, and hoAV they mi- 



brcntlicra ; comiiouudbieatliei-s. , -i • • i n n i c 



grate durmg periods ot floods, a lew 

 observations are necessary upon how they respire, as some 

 remarkable variations from the usual manner are observable, 

 evidently to enable certain tropical forms to resist causes 

 which arc not in existence in most extra-tropical regions. 

 Three modes of respiration are perceptible : first, the usual 

 one of oxygen obtained, except under peculiar circumstances, 

 from air in solution in the water, and which is separated 

 at the gills ; these may be termed for description, not defini- 

 tion, "water-breathers," as the carps, Cypriniiuv, or some of the 

 siluroids, as Ilacrones, and they can live, as a rule, without 

 rising to the surface. If any of these fishes are placed in a 

 globe of water at a moderate temperature, with a diaphragni 

 of net precluding their reaching the surface, their breathing 

 remains unaflected. If, on the contrary, a bandage is 

 stitched around the gill-opening, precluding their employing 

 their gills, they rapidly become sufibeated. This result in 

 another form is perceived to occur in India, either artificially 

 or naturally. Thus, Avhcn the Avater in which they reside 

 becomes suddenly changed from clear to very muddy, their 

 gills become choked, respiratioji is impeded, and death results. 



