APODES 



Eels, Morays 

 It is well known that the eel-like body-form has been acquired independently in 

 many groups of fishes and other vertebrates. The outstanding morphological feature of 

 the eel skull (Fig. S2J) is the reduction of the dorsal part of the opercular and the freeing 



soe 



epioi 



_ _ Lycodontis funebrls art 



lOp 



■preoperc 



Anguilla ro strata 



Fig. 82. Skulls of Apodes. A. Anguilla rostrata. B. Lycodontis funebris. 



of the pectoral girdle from the skull by the loss of the posttemporal. This result has been 



conditioned by the great development of the muscles that dilate the branchial chamber. 



This tendency is carried to an extreme in the moray (Fig. 825), in which the opercular 



apparatus has become almost vestigial. The gills too have become much reduced in size, 



perhaps because a smaller aerating surface is necessary on account of the "forced draught" 



of oxygen-bearing water. Or it may be that the "forced draught" apparatus is a response 



to a diminishing gill area. 



202 



