i DIPNEUSTI 515 
differs both in position and structure from its preoral analogue in 
the young of <Acipenser, Amia, and Lepidosteus. A month-old 
larva has much the aspect of a larval Newt. It has four pairs of 
vascular plumose cutaneous gills (Fig. 309), which are retained as 
Fic. 308.—Nest of the Protopterus of the Gambia. (From Budgett.) 
vestiges for a long time or even throughout life, and two pairs of 
synchronously-developed limbs. As an interesting instance of a 
nocturnal and protective change of colour, it may be mentioned 
Fia. 309.—Larval Protopterus on the seventeenth day. c, Cement organ ; c.g, cutane- 
ous gills; op, operculum ; p./, pectoral limb; pv./, pelvic limb; y.s, yolk-sae. 
(From Budgett. ) 
that the dark chromatophores of the skin of the larva expand in 
the day-time and the young Fish becomes darker in colour, and 
therefore less conspicuous when seen against a background of 
black mud or soil. At night the contraction of the colour-sacs 
renders the larva more transparent and probably less easily 
