3o8 A HISTORY OF FISHES 



sticky mucus, which adhere together to form a floating mass 

 of foam, dome-shaped or more or less flat on the upper surface. 

 In the case of the Httle Fighting-fish (Betta), the elaborate 

 courtship is followed by the surrender of the female, who 

 approaches her mate and is suddenly turned upon her side: he 

 then tightens his body around her, and turns her upside down, 

 but in a few moments the pressure is relaxed and the male 

 takes up his position below. The eggs are extruded, and after 

 being held for a few moments by the female to ensure fertilisa- 

 tion, are allowed to drop, and being heavier than the water, 

 they sink downward towards the waiting male. He catches 

 the eggs in his mouth, and swims upwards, gives them a coating 

 of mucus, and sticks them to the under side of the mass of 

 foam. From three to seven ova are extruded at a time, and 

 the process is repeated until some one hundred and fifty or 

 two hundred are produced. They are then guarded by the 

 father, who is obliged to keep a watchful eye on his mate, who 

 is not averse to eating them, if permitted. The larvae remain 

 adherent to the foamy nest for some time after hatching, and if 

 any of them should show a tendency to sink, they are caught 

 and replaced by the watchful male, until they finally drop off 

 when old enough to find food for themselves. The related 

 Paradise-fish (Macropodus) has very similar breeding habits, 

 but here the eggs are lighter than the water, and thus rise to 

 the mass of bubbles without the intervention of the male. 

 The female is completely inverted while the eggs are extruded, 

 and any which fail to adhere to the nest are collected by one 

 or both of the parents and placed in position. 



The Bitterling (Rhodeus), a small Cyprinid found in the rivers 

 of Central Europe, takes remarkable precautions to ensure the 

 safety of its offspring. The oviduct of the female fish is drawn 

 out to form a long tube, acting as a kind of ovipositor, by 

 means of which she deposits her eggs within the valves of 

 fresh-water pond mussels, where they are out of reach of 

 enemies. In this situation they undergo their development, 

 the respiratory current of water produced by the Shell-fish 

 serving to aerate the ova, and the fry finally leave their tempor- 

 ary host about a month after the deposition of the eggs. The 

 male fertilises the eggs after they have been extruded, and, as 

 Professor Cunningham remarks, "it is a most curious case of 

 adaptation of sexual instincts that the male is sexually excited, 

 not by the presence of the female of his own species, but by 

 the sight of the mussel in which the eggs have been deposited." 



