RATE OF GROWTH OF SOME SEA FISHES. 261 



himself has taken in the Elbe young shad of the following dimen- 

 sions : 



Middle of August .... 5-4 — 7*8 cm. 



First week in October . . . 6'9 — 8*6 „ 



Middle of October .... 7-7— 9*6 „ 



Middle of November . . . 8-0— 12-4 „ 



Ehrenbaura calls these specimens Finten, so that I suppose they 

 were identified as Clupea finta. He says that Hoek has recently 

 altered his former opinion, and now concludes that these young 

 specimens, which have already reached the permanent form, that is, 

 have finished their metamorphosis at the end of July, cannot be 

 derived from the spawn of the same year, but are already a year 

 old, and Ehrenbaum agrees with him. He goes on to state that in 

 the summer of 1891 he observed the spawning of the Finte in the 

 Elbe in the second half of May, and then obtained eggs with well- 

 developed embryos, and also larvae with large yolk-sacs. Towards 

 the end of May he captured numerous larvse of 8 to 9 mm. in length, 

 which retained a trace of the yolk, and on the 17th June larvae of 

 9 mm. to 1*4 cm. He obtained no more larvae, but in August got the 

 specimens above mentioned, which were taken in nets, and were 

 already fully scaled and had the form of the adult. He concluded 

 from this that the young larvae hatched in the river migrate to the 

 sea as soon as the yolk has been absorbed, only returning to the 

 river in the following year, at the size mentioned. This conclusion is 

 obviously erroneous. Supposing all the specimens to belong to the 

 species Clujpea finta, though it is not proved that they were not Clupea 

 alosa, we have to consider what is the size of the former species when 

 full grown. Day says it attains to 16 inches in length, so that it is 

 somewhat larger than the herring. Meyer has shown that the spring 

 herring spawned in April and May, have by the end of July for the 

 most part completed their metamorphosis, and are then 4"5 to 5'5 

 cm. long. What is there then to prevent the shad spawned in May 

 from completing its metamorphosis by the middle of August, and 

 reaching a length of 5'4 to 7*8 cm. ? The herring, according to Meyer, 

 is 8*4 cm. long and upwards by the middle of November, and yet 

 Ehrenbaum maintains that specimens of the twaite shad, a larger fish 

 when full grown, which are 8*0 to 12" 4 cm. long in November, are 

 eighteen months old. He compares his observations on the shad 

 with Hoffmann^s on the anchovy, and concludes that the shad takes 

 eighteen months to reach the same length that the anchovy reaches 

 in seventeen, regardless of the fact that the adult anchovy is scarcely 

 half the length, and much less than half the weight of the adult 

 twaite shad. 



NEW SEEIES. VOL. II, NO. III. 20 



