58 BULLETIN 188, UNITED STATES NATIONAL MUSEUM 



(1916-1923) makes no reference to this subject. Thanks to the ob- 

 servations made in Thailand in recent years, the egg-laying habits, 

 eggs, incubation, and development of this species are now rather well 

 known. From an account thereof published by the writer (1933b) the 

 following information is extracted : 



The existence, in a single fish, of eggs of several different stages of 

 development has been shown by dissection. It has also been proved 

 that only one ovary develops during one season. Whether the two 

 ovaries alternate in activity from year to year or whether only one 

 ovary ever functions remains to be determined. In numerous speci- 

 mens the mature ovary was found to occupy the left side of the com- 

 paratively small abdominal cavity, the digestive and other viscera 

 being pushed to the right side. 



It seems to be fully established that the care of the eggs devolves 

 only on the male fish. Throughout the hatching period the male is in 

 assiduous attendance. Human intruders are fiercely attacked and nat- 

 ural enemies, comprising for the most part small catfishes {Mystus of 

 Scopoli) and minnows {Rashora of Bleeker), are driven off. An 

 equally important duty of the male is keeping the eggs aerated and free 

 from sediment by fanning movements of the tail. In the sluggish 

 waters of swamps the eggs may become covered with sediment, which 

 prevents normal development and induces the growth of fungus. If 

 the guardian is removed, the eggs are preyed on by small fishes and 

 those that escape are coated with sediment and ultimately asphyxiated. 

 Fishermen sometimes take advantage of the male's devotion by fishing 

 at a stake or stump that has been found to bear eggs. By jigging with 

 unbaited hooks or using hooks baited with insects, shrimps, or small 

 fish, they sooner or later catch the male parent and sacrifice the in- 

 cipient brood. The female parent is never observed at the egg posts 

 under circumstances that indicate maternal solicitude. 



The number of eggs deposited at one time on one post may be several 

 thousand, and the ^gg output of one fish in a season may exceed 5,000 

 and even reach 10,000 or more. In Bung Borapet a four-sided stake 

 taken up for observation on July 17, 1932, was, by actual count, found 

 to have 1,733 eggs on two sides and approximately the same number 

 on the other two sides, a total of more than 3,400. The incubation 

 time, in water with an average temperature of 33° C, is 5 to 6 days. 



The Siamese Bureau of Fisheries has encouraged and facilitated egg 

 laying in this species by providing suitable posts. Thus, in May, June, 

 and July 1932 in an outlet of Bung Borapet, 53 round and square posts 

 were driven into the bottom at intervals of several meters in water 

 1.5 to 2 meters deep ; and on 18 days between May 3 and July 30, 36 

 of the posts were utilized by the fishes, 4 each on June 1 and 8 and 5 

 on July 2. Some eggs, removed from posts and stumps and placed 



