LARVAL FISHES : THEIR METAMORPHOSES. 137 



dorsal fin has developed unequally, dividing the 

 whole into two distinct parts, an anterior of great 

 size and a smaller posterior ; the upper jaw has in- 

 creased so as to project considerably beyond the 

 lower, whilst the teeth have disappeared ; the 

 long spines from the back of the head have 

 almost vanished, whilst the ventral filamentous 

 fins have become reduced in size. In the eye 

 there is a conspicuous relative decrease in size 

 from the earliest stage onward. The great size 

 of the eye is a feature of all vertebrated animals, 

 during the embryonic stages of their growth at 

 any rate. 



The young of the sun-fishes again present 

 some very remarkable features — of which there is 

 no indication in the adult forms — so much so that 

 there young have been described as of distinct 

 genera. The main features which characterise 

 them at this period is a series of sharp spines 

 projecting in all directions all over the body. 

 The adults are either smooth-skinned or covered 

 with minute prickles, according to the species. 

 Similarly, the young of one of the flying-fishes 

 {Dadylopterus), of the sea-perch (Serranus), the 

 " rockling " (Motella), and some others have passed 

 unrecognised, and have also been described as 

 distinct genera, their identity being so completely 

 masked. 



The young of the ribbon-fish (Trachypterus) are 

 remarkable for the very extraordinary develop- 

 ment of the fin-rays, exceeding that of any other 

 known fishes ; sometimes their fin-rays are many 

 times longer than the body ; moreover, these fin- 

 rays are provided with curious lappet or flange- 



