23 



gives a view of the growtli of the aniuial riugs in the scales of eels taken at 

 Struer on tlie 17th of August. In column A all the specimens examined are uoted; 

 O meaus tliat the specimens had no scales, 1, 2 etc. that scales were found and 

 that these showed the central zone only or this -f one to several concentric zones. 

 (In the followlng Tables also, tiie uumbers do not indieate the age of the specimen 

 but of its scales; the central zone is always taken as the Ist annual ring). In the 

 columns B, C and D in Tab. 3 are represeuted the eels of column A. which had 

 scales, arranged so that the crosses in B represent the specimens in which all the 

 scales examined were in process of growth, and those in D the specimens in which 

 growth of the scales had ceased; lastly, column C represents the eels in which 

 the scales were growing equally or had ceased to grow. — Thus the annual 

 rings were already on August ITth quite completely formed in some and were 

 nearly so in the majority. — Table 4 shows how far on the scales in larger eels 

 were in their growth at the same period; we hotice that in the silver eels they are 



cm. 

 42 

 41 

 40 

 39 

 38 

 87 

 36 

 35 

 34 

 33 

 32 

 31 

 30 

 29 

 2« 

 27 

 26 

 25 

 24 

 23 

 22 

 21 

 20 



Table 4. 



In the outlet at Struer. 



Haml net. 



X 



X X 

 XXX 

 XXX 





 X 



17th August lilDli. 



X =; growth of scalc concluded. 

 o = > > not conciuded. 



(^ = » » partly • , i.e. 



somc of thoso investi^ateil .still 

 jjrowinj; 



X 







X o 



o o o 



o 



X o o o 



X o o 



X X o o II 



completed nnich earlier tlian in the j-ellow eels. But even in the latter growth is 

 not for long, as we can scarcely find any eels in which the scales are still growing 

 towards the end of September; thus the new annual ring is completely formed at 

 the time the cold period of the year sets in. 



If one only becomes familiar with the slructure of the scales and their whole 

 appearance, it is extremely easy to see in them whether they are growing or not. 

 As mentioned above the underlying surface is seen in the latter as a distinct con- 

 tour or frame around the ontermost row of small piates; the latter likewise decrease 



