AQUARIUM FISHES 339 



some time out of water, so their tank must be kept carefully- 

 covered. 



The viviparous group of the Pcecilliid^ includes what 

 are probably the most attractive species of the family. The 

 fact that active, independent young are brought forth at 

 surprisingly short intervals, and that they are not at all diffi- 

 cult to rear, ensures their lasting popularity. There are 

 many species, of varying cplors, but all may be known by 

 the anal fin of the male, which ends in a needle-like process, 

 used as an intromittent organ. In most species the male 

 is much smaller than the female. 



The most commonly kept species, and probably the best 

 for the beginner, is Acanthopthalmus (Girardinus) guppyi. 

 This diminutive fish is a native of Trinidad and Venezuela, 

 and has been introduced in Jamaica and various other West 

 Indian islands because of its value as a destroyer of mos- 

 quito larvae. The males average three-quarters of an inch 

 to an inch, and the females up to two inches. The latter 

 are very plainly colored, but the males are extremely bril- 

 liant, presenting an amazing variety of patterns in metallic 

 greens, reds, blues and blacks, no two being exactly alike. 

 Most live-bearers are inveterate devourers of their own 

 young, but this species is not nearly so badly disposed 

 toward its offspring as most, and if the aquarium is well 

 supplied with vegetation a great many can be reared with 

 little difficulty. In case it is desired to save all of the young, 

 however, it is best to isolate prospective mothers, which are 

 easily distinguished. 



Most keepers of live-bearing fishes have their own 

 methods for insuring the safety of the young. Various 

 appliances are in use, ranging from small metal cages to 

 glass funnels, all intended to confine the mother while the 

 young escape through tiny apertures. It is far safer to 

 restrict the mother to a small part of the aquarium by 



