BUCCAL INCUBATION 131 



incubation, well known in point of time, but 

 not too familiar in personal experience. In 

 Ceylon it was first described by the Rev. B. 

 Boake (1 867-1 870) as occurring in the Siluroid 

 fish Arius falcarius, which has been determined 

 by Dr Francis Day to be synonymous with 

 Arius boakei. This fish frequents estuarine 

 waters and is very common in an extensive 

 backwater on the west coast of Ceylon called 

 the Panadure River. It has very large yolk- 

 laden eggs more than half an inch in diameter. 

 After being laid by the female they are found 

 nowhere except in the mouth of the male, where 

 they remain until they are hatched and until 

 the young have completely absorbed the yolk- 

 sac. I have observed that the intestine of 

 brood-nursing males is generally contracted to 

 narrow dimensions and empty, a fact which 

 was also noted by Day ; and as generally, the 

 palatine teeth of ovigerous males are greatly 

 reduced. In one case, however, which came 

 under my notice, where there were fifteen eggs 

 in the mouth, each containing an advanced 

 embryo, the palatine teeth were not appreciably 

 reduced and the hind-gut contained shell- fl^rw. 

 The opening of the oesophagus is constricted and 

 virtually closed, while the mouth and pharynx 

 are expanded to form a spacious brood-pouch, 

 where the eggs and young are exposed to a 

 constant current of water which passes over 



