190 THE INFLUENCE OF INANIMATE SURROUNDINGS. 



covers, to climb up palm-trees — Anahaa scandens. I have 

 certainly never seen this, though I have often caught Anahas 

 scandens in the Philippines. But the hypothesis that their 

 labyrinthine organs are merely auxiliary gills destined to en- 

 able the fish still to breathe through water when on land, finds 

 no confirmation in the observations made by the most esteemed 

 naturalists; indeed, it is quite incomprehensible how, in so minute 

 an amount of water as could find place within the labyrinthine 

 organ, so much oxygen could exist as the creature must con- 

 sume even in a few hours. And there can be no possibi- 

 lity of a renewal of the water deprived of its oxygen so long as 

 the animals live on land. It is, however, at this day, almost 

 superfluous to point out the absurdity of this early and often 

 disputed assumption by an analysis of the physiological pro- 

 cesses ; for the direct observations of Dr. Francis Day *^ — 

 known by his great work on the fishes of Malabar — have proved 

 that the accessory gill-cavities, or labyrinthine organs, as they 

 were called, of the Labyrinthici never contain water, but always 

 air only. So that these organs must be simply designated as 

 organs for respiring air, i.e. as lungs which have been formed 

 by modification of a portion of the water-breathing gill-cavity ; 

 the fishes that have them are therefore to be regarded as Amphi- 

 bians with quite as much reason as toads and frogs, or even 

 better, since they are capable of changing the nature of their 

 respiration — of air, that is, or of water — at will and suddenly 

 without any interruption ; nay, are actually accustomed so to 

 change it. Finally, in some Brazilian fishes — Sudis gigas, Ery- 

 thrinus tmniatus and hrasiliensis — the air-bladder, as Jobert 

 has lately discovered, serves directly as lungs subsidiary to the 

 gills, since they inhale air through a connecting passage which 

 subsists between the throat and the aii--bladder. If this air- 

 passage (ductus pneumaticus) is ligatured, the fishes die of 

 sufibcation, since the amount of air obtained through the gills 

 does not suffice them for respiration. By these observations it 

 is made intelligible how an air-bladder could be transformed 

 into a lung. Insufficient absorption through the gills brought 

 the fish to swallowing air ; instead of passing out through the 

 gill-openings, as in other fresh-water fishes, the air passed into 



