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 

 these 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- 



