RAtE OF GROWTH OP SOME SEA FISHES. 235 



separated by no evident limit. Meyer^ therefore, measured the 

 growth by taking- the lengths of the smallest fish in each catch. 

 Thus the growth of the smallest fish is shown by the following 

 figures : 



This gives an increase of 1"0 cm. per month, but of course, since 

 the variation in size of fishes of the same age is considerable, the 

 mean growth of the young from the spring spawning was somewhat 

 greater. Two rearing experiments made by Meyer for comparison 

 gave a mean result of 1*07 and I'l cm. per month respectively; 

 the experiments lasted four and a half and three months respectively. 



Concerning the autumn herring, which spawns in the open sea in 

 September and October, Meyer has no very conclusive observations, 

 but the evidence he has indicates that the growth of these is equal 

 to or rather greater in one year than that of the spring herring, the 

 adults being somewhat larger than in the case of the latter. He 

 points out that some herring spawn later than October, even as late 

 as December, so that it is impossible to separate the broods with 

 certainty. He also remarks that the spring herring, between six 

 months and a year old, are not definitely separated in size from the 

 smallest autumn herring of the preceding autumn ; and as he took 

 the smallest specimens only for his measurements, we must conclude 

 that the average size of spring herrings at one year old is greater 

 than 5"4 inches ; we may, perhaps, put the average size at 6 to 6| 

 inches, and the maximum at 7. 



Meyer proceeds to discuss the amount of growth in the second 

 year, and the age at which puberty is attained in the herring. In 

 his collection, the smallest ripe herrings were 20 cm. long (7"9 inches) 

 while those of 21 to 22 cm., were not rare. Ljungmann states that 

 some herrings off the coast of Sweden are ripe at 17"5 or even 16 

 cm. length. Meyer argues that, taking 20 cm. as the limit, the year- 

 old fish have only 6 or 7 cm. to add to their length in order to 

 reach it. But he regards it as impossible that the young of the 

 spring-spaAvning herring should become autumn-spawning herring 

 or vice versa, and since the majority of the herrings which spawn 

 for the first time are more than 20 cm. long, he believes they spawn 

 first at two years old. Meyer does not mention the consideration 

 that an increase of half the total length may, and generally does 



