33 



as the real maximum of the group; it now lies considerably higher, as will appear 

 later. — The upper limit of the group is far more difficult to determine; tliat it 

 agrees with the scale-limit iu spring and must therefore be placed between 17 and 

 18 cm. follows from what has been said earlier on the upper limit of the I group 

 in autumn, aud appears further very distinctly from Table 8, cols. 1 and 4 aud 

 Tab. 7, cols. 3 and 4; but when growth progresses, the measurementmethod is 

 110 longer of use, partly ou account of the difficulties of obtaining material, partly 

 because this and the following year's group cannot be separated into 2 groups by 

 this method. To find the limit which divides the II and III groups iu autumn 

 we must therefore investigate the scales. 



It has been mentioned on an earlier oecasion, that these are laid dowii in 

 the skin of the eel when it becomes ca. 18 cm. loug, which again indicates that 

 it is just the specimens of the II group which begin in summer to form the cen- 

 tral zone of the scale, the growth of which is ended in autumn. 



As specimens of a year's group even at this size keep together somewhat 

 in growth, it is a highly probable supposition that at any rate the great mass of 

 them will also form their scales iu the same summer. This view coiifirms, for 

 example, what we found fairly distinct in Tables 7 and 8, (1) that the upper limit 

 of the II group in spring is ^= the scale-limit, (2) that its great mass passes this 

 limit in the course of the period of growth, so that the maximum of the group 

 is to be found over ca. 20 cm. at the end of this period, and (3) that its lower 

 limit is the scale-limit at this time. 



It is thus by a combination of our two methods, that we succeed in being 

 able to determine the limits of the II group in autumn, or what is the same: the 

 limits of the III group in the following spring before growth begins. The measurement- 

 method shows us, that the »mass« of the group passes the scale-limit in the course of 

 summer, so that its maximum is to be sought for above this; but it cannot deter- 

 mine this poiut exactly; bj' meaus of the scale iuvestigatious, however, we find 

 both the limits and even the maximum of the group (see Tables 3 and 9). Thus 

 all the specimens iudicated by 1 in Table 3 are of the II group, which have 

 indeed scales but have not completed the growth in length, so that the maximum 

 the Table shows would be higher at the end of the period of growth. In Table 9 

 the group is seen in the following spring; as it is after the date of immigration, 

 it is now cailed group III; but its limits and maximum are still as iu September — 

 October of the previous year when it was known as the II group. 



Whilst the average growth of the eel in the first year is 1 cm., and 

 o cm. in the second, it is ca. 10 cm. in the third; after this the yearly growth 

 again becomes less. 



The growth of the eel in the fourth year aud onwards is very clearly 

 shown in the tables. 



In using these it has to be remenbered, that the figures 1, 2, 3 etc. indi- 

 cate the number of annual rings in the scales, i.e. the age of these and not of the 

 eel, which is found by adding 2 after the necessary correction to the point of 

 starting. From the middle of .July this is absolutely necessary, as the new zone 



