58 NEW YORK AQUARIUM NATURE SERIES 



known commonly as fish-pox. Eventually the cysts or swellings 

 break and numerous spore-like cells are liberated. As it is by 

 means of these spores that the disease spreads, the affected fishes 

 should be removed as soon as the swellings make their appear- 

 ance. There is no specific for this disease, but the cysts may be 

 lanced, and peroxide of hydrogen or the stronger solution of po- 

 tassium permanganate introduced into the wound with a small 

 pipette. If the cysts are small and not too near a vital part, the 

 fish sometimes recovers without treatment, but, as a rule, the 

 disease is fatal. Both fresh and salt water fishes are attacked by 

 these protozoan parasites, but fortunately the cultivated forms 

 of aquarium fishes are seldom aflfected. Wild fishes, such as min- 

 nows, killifishes, etc., may have the disease in its early stages 

 when taken, and, if later the swellings which cause the disease 

 should make their appearance, the aflfected fishes should be iso- 

 lated at once for treatment, or if not valuable it is better to 

 destroy them. 



THE CA'iE OF YOUNG FISHES. 



The breeding habits of aquarium fishes vary to such an 

 extent that it is practically impossible to lay down any general 

 rules to cover all cases. Nor is it possible here to more than out- 

 line the methods of treatment for a few of the many species. 



According to their manner of reproduction, fishes naturally 

 form two classes. Some species, such as the goldfishes, stickle- 

 backs and chanchitos are oviparous and lay eggs which later 

 hatch out into the young. Others, like the swordtailed minnows 

 (Xiphophoriis) and topminnows (Gamhusia) , are viviparous or 

 live-bearing and bring forth living young. Practically all fishes 

 are cannibalistic in habit at certain stages and do not hesitate to 

 eat even their own young. In the case of the live-bearing fishes, 

 a good method of protecting the young is to place a plate of glass 

 m a slanting position in the aquarium so as to shut ofl^ the adults 

 at one side. The glass should fit loosely enough so that the young 

 fishes can find their way into the body of the tank past the'^edges 

 of the glass, while the adults are unable to do so. After the birth 

 of the young, the adults should be removed to another jar. The 

 swollen appearance of the female is an indication that the pre- 

 hmmary arrangements should be made. 



In the case of the nest building oviparous fishes, such as the 

 sticklebacks and chanchitos, the eggs are cared for by the adults 



