The Age and Groivth of some Eels from a Worcestershire Pond. 11 
What I have said about the voraciousness of the eel applies 
only to the yellow eel, as the silver eel does not take food, at least 
usually, and one nearly always finds their stomachs empty. 
There is a great difference between the flesh of the yellow and 
the silver eel, for the latter is much firmer, and I think that any- 
one used to handling large quantities of eels could pick them out 
blindfolded. 
The silver eel has nearly reached its full development and has 
accumulated fat in its tissues before commencing the long voyage 
to its Atlantic spawning ground, and we know that in other fish 
the development of the sexual products takes place at the cost of 
other tissues — for example, the great difference between a salmon 
entering a river to spawn and a spent kelt. The silver eels are 
actually sold at higher prices than the yellow ones. 
The methods usually employed to ascertain the age of fish are 
the enumeration of the zones of growth of the scales, otoliths and 
vertebrae, much the same as can be done with sections of trees. 
With some fish the scales give the best results, with others the 
otoliths or vertebrae, as also the operculum, but one can always 
succeed with one of these methods. 
In the eel the scales were first used for finding the age by 
Gemsoe, and Ehrenbaum later proved that the otoliths give the 
best results ; but it is always interesting to compare the difference 
between the number of zones on the scales and the otoliths in eels 
taken from various places. 
The structure of the scale of the eel is different from that of 
most other Telerstean fishes, and consists of a more or less oval 
plate of fibrous tissue. I cannot better describe its structure than 
by quoting from “ British Fresh Water Fishes ” by C. Tate Regan, 
1920, p. 162 : 
“ When a scale is examined under the microscope the outer 
surface is seen to be studded with little calcareous buttons, which 
are arranged in zones or rings parallel to the edges, and are 
separated from each other by narrow rings occupied only by the 
fibrous ground substance of the scale. This structure is due to the 
fact that the eel feeds and grows actively in the summer months 
only, and the zones are annual rings formed during the summer, 
whilst the narrow interspaces represent the growth of the scale in 
the colder months.” 
The first scales appear above the lateral line near the anus, and 
therefore the scales taken from this region are the oldest, and they 
are not formed until the eel has attained a length of from 15-20 cm. 
The centre of the scale is, like the interspaces, devoid of calcareous 
buttons, and I call the middle zone, which is first formed, the 
central zone. 
Fig. 1 represents a scale taken from a silver male of 37 cm. and 
52 grams, with a central zone C and four others, in all five zones. 
