Fish-Hatching in the Aquarium 319 



oughly exhausted. Whenever this happens 

 we may be certain that the aggressor is of 

 the male, the chased or persecuted fish of 

 the female sex. 



While a superficial observation may not 

 disclose the difference between the sexes, 

 certain characteristics are known to exist, 

 by which they can be recognized. The male 

 fish, when ready to mate, shows a peculiar 

 depression near the cloaca, just as if a small 

 piece of flesh had been pinched out. On 

 the gills of some species small convex spots 

 of a grayish color make their appearance 

 and remain during the mating period. Both 

 these peculiarities are absent in the female 

 fish. The latter is, instead, considerably 

 stouter in body, so much so that the differ- 

 ence between the sexes is quite evident. 



Soon after the male has selected his mate, 

 the actual spawning process takes place. 

 For the depositing of the spawn, plants are 

 usually preferred to anything else. As 

 soon as the female finishes spawning the 



