202 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



no guide, as it has not taken up its final position. The 

 relative differences in the beginning of the dorsal and 

 pelvic fins in the adult sprat and herring are quite 

 different from what is found in young stages under 43 

 millimetres. The beginning of the pelvic fins in adult 

 sprats is usually distinctly in front of the dorsal fin. In 

 the case of the herring, the dorsal fin starts in front of 

 the pelvics. Ehrenbaum's figures in " Nordisches 

 Plankton " show that young herring up to 34 millimetres 

 in length have the pelvic fins well in front of the dorsal. 

 It is evident, therefore, that the dorsal fin must change 

 its position and gradually advance nearer the head as the 

 fish grows and the scales make their appearance. This 

 advance of the dorsal fin may not be completed till the 

 young herring reaches a length of 47 millimetres, as 

 shown by the table giving the measurements of the fish 

 collected on May 28th. The only way to distinguish 

 young herring from young sprats before the transforma- 

 tion is complete is by examining considerable numbers of 

 fish. Young scaleless herring can be readily separated 

 from young sprats when mixed up with them, by their 

 bodies being much narrower and ribbon-like. 



The following tables give the size of the fish, 

 measured from the tip of the snout to the end of the 

 caudal fin, the distance of the dorsal and pelvic fins from 

 the snout, and the difference in the position of the 

 beginning of the pelvic fins from the snout compared 

 with the dorsal fin. The photographic illustrations 1-10 

 represent a typical fish from each sample, 11 and 12 the 

 two extreme sizes from a sample collected on May 28th, 

 13-16 fish of nearly the same length but different 

 character in a collection taken on July 17th. 



The illustrations of fish of nearly the same size but 

 different character are useful in showing the marked 



