XVIII 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. PP. 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 Polypterus 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 
Fie. 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 River Gambia, Budgett” was fortunate in 
securing a larva of P. senegalus, 1 to 14 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. vil. 1901, p. 330. 
2 Trans. Zool. Soc. xvi. Pt. ii. 1901, p. 118; also footnote on p. 317. * p. 290. 
