CROSSOPTERYGII 483 



pectoral fins. According to the same observer, the air-bladder 

 is an accessory respiratory organ, supplementary to the gills, 

 rather than a hydrostatic organ. 



In P. bichir the eggs ripen from June to September, inclusive, 

 and, as in most other Nile Fishes, the breeding season is during 

 or just after the period of inundation. P. senegalus and P. 

 lapradei spawn during the rainy season in the months of July, 

 August, and September, but nothing is certainly known as 

 to the place or mode of deposition of the eggs. During the 

 breeding season Polyioterus is unusually active and excitable, 

 and at this period the anal fin of the male becomes greatly 

 thickened and enlarged, and has its surface thrown into deep 



Fiu. 280. — Map showing the distribution of the Polypteridae. 



folds between the successive fin-rays.-* The use of the modified 

 fin is not known. During his stay at McCarthy Island, about 

 160 miles up the Eiver Gambia, Budgett^ was fortunate in 

 securing a larva of P. senegalus, 1 to 1;^ inches in length, or 

 only about one- third the length of any larval Polypterus previ- 

 ously known (Fig. 281). The larva is described as a most 

 beautiful object, " marked with black stripes on a golden ground, 

 with a conspicuous golden stripe on each side above the eye, 

 across the spiracle, and along the dorsal surface of the external 

 gill." The pinnate external or cutaneous gills were relatively of 

 much greater size than in the considerably more advanced stage 

 figured elsewhere,^ and reached half-way to the tail. The dorsal 

 fin is not divided into finlets, and behind it is continuous with 

 the caudal, while the anal fin is scarcely distinct from the 



1 Budgett, Trans. Zool. Soc. xv. Pt. vii. 1901, p. 330. 

 ^ Trans. Zool. Soc. xvi. Pt. ii. 1901, p. 118 ; also footnote on p. 317. ^ p. 290. 



