DIPNEUSTI 



515 



differs both in position and structure from its preoral analogue in 

 the young of Acipenscr, 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 



FIG. 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 



c op. y.s 



Fio. 309. Larval Protopterus on the seventeenth day. c, Cement organ ; c.g, cutane- 

 ous gills; op, operculum ; p. I, pectoral limb; pv.l, pelvic limb; y.s, yolk-sac. 

 (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 



