63 



narrow or low. Passiug over froni the larval condition into that 



of a youug iish its height sooa iucreases coüsiderably as is shown 



by the followiug table : 



A larva of a lcui,4li of 20 iii.iu. lias a licight ol 1 iii.iii. 



., » » » „ 21. „ „ „ „ „ IM „ 



» » ,. i> .» 27 „ „ „ „ „ 1.8 „ 



„ » „ » » 28 „ „ „ „ „ 2 



» » » » u -^J »> » >J )J ,j 'i-* )> 



» .) ,) » » '^2.5 „ „ „ „ „ 2.8 „ 



» » )j » » 'J'J » )j » » j» <J-2 » 



„ » » ,. ., 34 „ „ „ „ „ 3.3 „ 



a young herring „ „ „ „ 36 „ „ „ „ „ 4.75 „ 



„ „ » )j » » >j 37.5 „ „ „ „ „ o „ 



„ „ „ „ „ ,. „ 40 ,, „ „ „ „ G.7 „ 



We see {'rom this list that, when a herring-larva of 34 m.m. 

 chauges iuto a youug herring of 40 m.m., a change of leugth of 

 about 18°/o happens to take place, with a change in height from 

 3.3 into 6.7 ra.m., i. e. of over 100%. Some of the little fish of 

 36 m.m., and distinctly all those of 37.5 m.m. show the be- 

 ginniug of the formation of a scaly covering ; at the same time 

 the embryonic pectoral fins begin to retire and to make place 

 for the norraal ones ^). 



It is thus shown that the herring of the Zuiderzee , like the 

 spring-herriug of the western Baltic and those of the little river 

 Schlei change the larval condition in that of the young fish after 

 having aquired a length of 35 a 36 mm. The herring-larva of 

 the Northsea on the contrary reaches a length of 46 a 48 m.m. 

 before uudergoing its metamorphosis and assuming the lasting 

 shape of the young fish. In the eastern Baltic a herring spawns 

 in water the saltness of which is considerally higher than is the 

 case in the western Baltic ; it there spawns in antumn and not 

 in spring, as does the herring of the western Baltic, of the 

 Schlei, and as we have seen that of the Zuiderzee; there the lar- 

 vae attain a length of 45 m.m. before assuming the appearance 

 of a little herring. So it would have been possible, only judging 



1) I have given a description of the metamorphosis of the pectoral fins and of other 

 changes taking place during the development of the herring in the Report on fishing 

 with .Ankerkuileu". Brjlage C. [1888]. 



