•aquatic Ette 



71 



posed to the air, and it is hardly possible 

 to find a better example than the gills 

 of a fish. At first sight they look like a 

 series of comb-like organs, scarlet with 

 the blood that is seen through their deli- 

 cate coverings; but if they are closely 

 examined, they will be found to possess 

 a most beautiful form, exposing a very 

 large surface, and at the same time occu- 

 pying a very little space. Each tooth of 

 the comb is composed of innumerable 

 plates of membrane, traversed by the 

 blood vessels, and admitting the air on 

 both sides. In fact the gills remind the 

 observer of the leaves of a slightly closed 

 book, in which a very large amount of 

 surface is compressed into a very little 

 space. 



I have been particular in describing 

 these gills because they demonstrate the 

 real action of respiration better than any 

 structure tbat can be found. Moreover, 

 they can easily be obtained, and an ordi- 

 nary magnifying glass is sufficient to ex- 

 hibit their wonderful mechanism. 



The manner in which a fish breathes is 

 simple enough. It opens its mouth and 

 admits a certain quantity of water, just 

 as we admit air into our lungs. It then 

 closes its mouth and drives the water out 

 at the gill-covers, causing it to wash over 

 the gills in its passage. The oxygen con- 

 tained in the water thus comes in con- 

 tact with the blood, and so the fish man- 

 ages to breathe. 



When the fishes in the aquarium re- 

 main persistently at the surface, "suck- 

 ing air" in common parlance, it is an indi- 

 cation of a lack of oxygen in the water, 

 which may be due to pollution or over- 

 stocking — more fishes than the plant life 

 of the tank can support. When a tank 

 approaches this condition, we are told 

 by aquarists more enthusiastic than accu- 

 rate, that the fishes are taking the air and 

 passing it over the gill capillaries, and 



that in the procedure the delicate organs 

 are "burned" by the raw air. On the 

 contrary, the fishes are merely gurgling 

 the air and water in the mouth, thus 

 charging the water with oxygen ; the air 

 is regurgitated (passed out through the 

 mouth), while the charged water passes 

 back over the gills in the normal way. 

 In other words, the fish is endeavoring 

 to oxygenate the water in the same 

 fashion as when the aquarist dips a cup- 

 ful from a tank and pours it back for the 

 same purpose. 



Overstocking is a fault almost con- 

 fined to the beginner. The experienced 

 aquarist realizes that the welfare of his 

 fishes is as dependent upon ample water- 

 volume per fish as it is upon the proper 

 foods. Rather than try to keep as many 

 fish as possible in a given tank, he en- 

 deavors to give each fish as much water 

 as his equipment permits. An aquarium 

 should never be so thickly populated that 

 a rise of temperature will cause discom- 

 fort due to the rapid diffusion of oxygen 

 into the atmosphere. Water will hold 

 more oxygen when cool than when warm. 

 A rise of temperature of 16 degrees in 

 a tank will result in a loss of half of the 

 oxygen it was able to retain at the lower 

 point. Thus the capacity of an aquarium 

 should be based upon the highest tem- 

 perature to which it is apt to be sub- 

 jected, and rapid fluctuations may be ex- 

 pected if the vessel be small. Safety first 

 among aquarists means too few rather 

 than too many fishes. 



Tbe American Federation of Goldfish 

 Fanciers has merged with the Brooklyn 

 Aquarium Society, the members having 

 been elected to the latter organization in 

 a body. 



He that would catcb fish, must ven- 

 ture bis bait. 



