17 



leaves as deposit sonie fine threads of orgauic substauce, in which some very 

 small calcareoiig grains are seeii.« 



Lastl}', B. mentions tliat the scale of the eel develops late; he has 

 not found any on au eel of 7 cm. iu length. And he condudes his descriptiou 

 of the scales of the eel by saying, that they are specially well adapted to the study 

 of the development of the scale. He lacked the material at that tune but hoped 

 to procure it later. 



To this description by Baudelot I may add sorae remarks on the concen- 

 tric zones. One might think, for example, that they always had tlie same breadth 

 in the same scale, but this is not the case; the number of rows of small piates 

 (medalhous) within the different zones varies greatly. — Nor can these ahvays be 

 correctly described by the term rings. Sometimes the zone is only developed as 

 a kind of cap at both ends of the scale's longitudinal axis, so that nothing of this 

 zone appears in the scale's transverse axis. The probability is that iu these cases 

 we have to do with a restricted formation for the year; the specimen has not 

 succeeded in forming any connection between the two caps, before the period of 

 growth ended. This is indicated especially b}' the faet, that in the sil ver eel we 

 often find the outermost ring represented by these two caps, which I have also seen 

 in formation and growth; and iu this the growth of the scale ceases earher iu 

 summer thau iu the yellow eel, so that there is actually less time for the formation 

 of rings — which results therefore in their incompleteness. — But this imperfect 

 ring-formation may also often occur within the scale between other fully developed 

 rings. In accordance with what has beeu said above, they must always be included 

 in determining the age of the scale (and of the eel). 



The scaly coveriug of the eel (by Chr. I). Lunn). 



The appearance of the scaly coveriug iu the eel is very variable in the 

 different speeimeus and varies constantly with the age of the individual. Eveu if 

 most of the scales are laid down at the same time (iu the same summer), this 

 rule is far from being without exceptions. 



I choose for descriptiou here a single specimen which I consider to be 

 typical, and take therefore au »8 years-; old, female eel (the oldest scale has 6 

 auuual rings). 



Ou a broad helt above and below the lateral line the loug, narrow scales 

 lie in two directions at right-angles to oue another, forming quite siiort rows, in 

 which the scales lie parallel to oue another; as the rows form angles of 90" with 

 one another, this part of the skin has a peculiar, chequered appearance. Almost 

 all the scales are here of the same age (all show 6 annual rings), but we find 

 exceptionally smaller and youuger scales in the outermost of the rows mentioned, 

 which iu general contaiu 6 — 10 scales (rarely up to 18 — 20). — ■ Ventrally the 

 scales lie ouly in oue direction, and the nearer we approach the veutral margin 

 the more is this direction parallel to the longitudinal axis of the fish; here the 

 scales are also younger (4 — (3 auuual rings, some eveu fewer). Dorsally the scales 

 also decrease iu age, the scales in the outermost part of the helt mentioned (and 



