AQUARIUM FISHES 337 



popularity is rapidly increasing. Many aquarium societies 

 have been formed for the importation of specimens and the 

 dissemination of knowledge concerning their care. Every 

 large city has dealers who specialize in fishes of this sort, 

 and a little investigation will reveal their whereabouts. 



Many of the tropical species are of surpassing beauty, 

 and there is a great range of curious breeding habits. They 

 are by far the most fascinating of aquarium fishes, and 

 most are really no more difficult to maintain in health than 

 goldfishes. The chief requirement is a uniform tempera- 

 ture, ranging from 60° to 75" Fahrenheit. Tanks are made 

 with heating apparatus attached, and these may be useful 

 at times. Ordinarily they are unnecessary, except for very 

 delicate fishes, for once they have become well acclimatized 

 most species are very hardy, if a steady warmth is main- 

 tained. 



Unfortunately, most of these fishes, like many plants, 

 especially the orchids, have not yet been given suitable com- 

 mon names, and are known by their scientific appellations 

 only. A little application, however, will overcome this diffi- 

 culty, and the amateur soon speaks them as glibly as the 

 most hardened expert. Perhaps the most interesting group 

 is the PcECiLLiiD^E, or Killifishes. About two hundred 

 species are known, and are divided by aquarists into two 

 groups: oviparous, or egg-laying forms, and viviparous, 

 in which the eggs are retained within the body of the parent 

 until they are fully formed, and the young able to care for 

 themselves when emitted. 



Of the egg-laying group, the species of the genus Fundu- 

 Itis are very numerous, and extend from Maine to Central 

 America. It is represented on the eastern coast by a num- 

 ber of well-known species, some living in brackish water. 

 The Common Killifish (F. majalis) and the Fresh-water 

 Killifish (F. diaphanus) are very abundant, and will live 



