FRESH-WATER FISHES OF SIAM, OR THAILAND 469 



The eggs, 1.25 to 1.5 mm. in diameter, owe their buoyancy to the 

 presence of a large oil globule. They float flush with the surface, have 

 a rich yellow or amber color, and are usually mixed with small leaves 

 and bits of vegetable matter such as is ordinarily found in quiet, shal- 

 low, weedy waters. 



Incubation is rapid and is completed within 3 days, varying within 

 narrow limits with the temperature of the water and the amount of 

 direct sunlight. On the day of hatching the larva is 3.5 mm. long. 

 In 4 days, at a length of 6.75 mm., the larva leaves the surface and 

 swiins freely at different levels, and respiratory movements have begiin, 

 although with the cessation of active effort the larva rises to the surface 

 and cannot remain at the bottom. By the end of the fifth week, having 

 reached a length of 10 to 12 mm., the larva can live comfortably at 

 or near the bottom of a small aquarium, and go to the surface at short 

 intervals to take in air. With the coming of the ninth week, having 

 attained a length of IT to 20 mm., the young goes to the bottom, hides 

 in the mud, and thenceforward assumes the habits of the adult. 



A fish about 6 cm. long, carried from Bung Borapet to Bangkok 

 early in 1932, was kept in an aquarium with other fish of the same 

 lot and on September 20, having attained a length of 21 cm., spawned. 

 The eggs were removed to a separate tank and hatched September 22, 

 the young shortly after hatching being 4 mm. long, with a brown yolk 

 sac 1.8 mm. long. When at rest the young remained at the surface of 

 the water with the yolk sac uppermost, the long axis of the body 

 being parallel with the surface ; they were able to maintain themselves 

 on the bottom or below the surface only by active swimming effort. 

 On September 23 some of them began to swim with the back uppermost, 

 and by September 25, having reached a length of 7 mm., most of them 

 had assumed the upright position. 



The fish is carnivorous and subsists on a variety of living creatures, 

 including fish, frogs, snakes, and insects. While ordinarily it is read- 

 ily taken by hook and line, the male fish cannot be caught during the 

 period when it is protecting its eggs and young. A very simple trap 

 desig-ned especially for use at that time consists of a wide-mesh bamboo 

 cone kept in place by a small stake or wooden pin stuck into the bottom. 

 Although one of the astute fresh-water fishes, Ophicephalus striatus 

 tries to pass through the trap and is unable to disengage itself. 



The fish has the regular habit of settling in the bottom mud of lakes, 

 swamps, and canals as the waters dry up and of going deeper and 

 deeper into the mud as desiccation proceeds. As long as the skin and 

 breathing apparatus keep moist, the fish can survive without water for 

 a number of months, occupying pockets in the stiff mud sometimes 

 nearly a meter below the surface and subsisting on the stored fat until 

 the rains set in. 



590087—45 31 



