SEA- FISHERIES LABORATORY. 203 



distinctions that occur. The two lower fish are young 

 sprats measuring 37*4 and 373 millimetres in length. 

 The dorsal fin of the slightly larger one is 05 millimetre 

 further away from the tip of the snout than the pelvics. 

 The pelvic fins in the smaller one are 0'2 millimetre 

 further away from the snout than the dorsal. The fish 

 are moderately deep and the scales are developing. I 

 regard the two upper fish as young herring. The first 

 one is 34'6 millimetres long. The second is 38'9 milli- 

 metres in length. The dorsal fin of the former is 

 2'5 millimetres further away from the snout than the 

 pelvics. In the latter it is 2*3 millimetres further away 

 from the snout. Both fish are narrow and ribbon-like, 

 and were probably almost transparent when alive. The 

 scales are not developed. These characters agree well 

 with the description of young herring of this length given 

 by Ehrenbaum. If Ehrenbaum's identification of the 

 young fish is correct, it is quite clear that considerable 

 change takes place in the position of the dorsal fin in 

 relation to the pelvics before the final characters are 

 visible. The dorsal fin represents part of the remains of 

 the embryonic fin which extended along the whole of the 

 back, round the tail and along the ventral margin. The 

 embryonic fin gradually disappears as the larva grows 

 till only the persistent parts known as the dorsal, caudal 

 and ventral fins are left. The pelvic fins are appendages 

 developed after the transformation of the embryonic fin 

 is completed, but before the dorsal part becomes a fixture, 

 and are distinct outgrowths from the body. Their 

 position is probably nearly permanent all through the life 

 of the fish. As the fish grows in length and depth the 

 dorsal fin is gradually pushed forward, and finally 

 becomes attached to some of the dorsal spines of the back- 

 bone just above the pelvics. 



