Fig. 6j. Molliciicsia pctciisis 

 (Life si:i'l 



There are two nther forms of Mollienesia used largely in the aquarium, 

 ,1/. latipiiiiia and .1/. z'clifera, the principal external differences being in the size of 

 the dorsal hn. The aliove shows the handsomest and rarest variety. The male has 

 the extraordinary dorsal development, but the fin is only held fully erect in moments 

 of excitement, at which time he is strikingly beautiful. Darwin, in "The Descent of 

 Man," refers to this fish on account of the great difference in appearance between 

 the male and female. The young are born alive. Those shown in illustration are 

 alxiut twelve weeks old. MoUienesias are naturally salt or brackish water fishes. 

 They become fairly well acclimated to fresh water, but do not stand much disturb- 

 ing after once being settled in an aquarium. Slightly brackish water suits them 

 better. Specimens bred In captivity seldom attain the highest development of the 

 dorsal fin. 



Figures 65 to 71 all have their young born alive. .\s the male reaches the breed- 

 -"-- -•■" the anal fin develops into an organ of intromission. This easily distin- 



guishe 



the sexes. See pages 257 (B 9) and 260 (N 2). 



80 



