WHOLESALE BREEDING 71 



A continuous warm temperature is imperative for some species 

 and for these it is not worth while attempting to breed outdoors in 

 a temperate climate. 



In selecting a stock to breed from for conunercial purposes it is 

 inadvisable to choose the species which have already become common, 

 even though they are easy to breed. It is much better to pay more for 

 something out of the ordinary if there seems to be a reasonable chance 

 of breeding it. The "fashions" change so rapidly in tropical iishes 

 that we could not attempt here to advise what to breed, as our book 

 would l)e likely to look old by the time it is off press. 



Sex in Tropical Fishes. A\'ith live-ljearing or viviparous hshes 

 the se.xes are easily told b)' the anal lln of the male having developed 

 into a sexual organ, liven before this development has taken place 

 it will be found that the anal fin at an early age is slightly more pointed 

 in the young males. In the adult females there is a dark s])ot in the 

 bod}', just above the venl, caused b_\' the presence of }oinig not yet 

 delivered. 



The means of identifying the se.ves in the egg-dropping troijicals 

 are not so obvious and must be confined to generalities. The com- 

 parative fullness of the female prior to spawning, the pursuit of the 

 females bv the males, the Ijrighter coloring of the males are all points 

 which we look for. With many fishes the fins of the males are a 

 little longer and more pointed than in the female. 



There are many wild iishes from lioth tropical and temperate 

 climates whose sex is impossible tu determine from external observa- 

 tion. Even in studying the matter by dissection the microscope must 

 sometimes be brought into play when the fishes are out of breeding 

 season. 



