294 BRITISH FRESH-WATER FISHES 
In colour the common eel varies considerably according 
to season and nature of habitat. Sex, also, probably affects 
the skin tints, but that is still very uncertain, by reason that 
the organs of reproduction are so exceedingly small while the 
fish remains in fresh water, that it is only by aid of the 
microscope that male and female can be distinguished. The 
back of the fish is dark olive-green, sometimes tending to 
brown. Below the lateral line the tints become either golden 
or silvery, and the under-parts are white. In one respect the 
eel is almost unique among fishes: it always seems to be in 
good order, firm and plump—if plumpness is a term applicable 
to a creature measuring fourteen or fifteen times as much in 
length as in depth. 
The northern limit of the eel in Europe has been fixed by 
Dr. Ginther at 64° 30’ North latitude. It exists all round 
the Mediterranean, but, strange to say, is not found 
Distribution, . : 
in the Black and Caspian Seas. On the American 
coast of the Atlantic it meets with other species, but does not 
extend to the Pacific watershed. In Britain it may be said 
to exist everywhere. 
The life-history of eels has been an attractive mystery to 
man ever since he began to indulge curiosity about the ways 
of his humble fellow-creatures, yet it is only within 
the last quarter of a century that any certain light 
has been thrown upon their domestic arrangements. Aristotle, 
baffled in trying to solve the enigma of their reproduction, 
had recourse to the unphilosophic theory of spontaneous 
generation, the outcome of putrefaction. Gesner (1516-1565) 
could suggest nothing better, and even at this day there are 
people in this country who believe that eels may be produced 
by steeping horsehair (the hair of a stallion for choice) in 
water. Yet one can scarcely afford to smile at such simplicity, 
seeing that, down to 1896, scientific ichthyologists classed eels 
in the larval stage as a distinct order, or at least a distinct 
family, of fishes under the title of Lepsocephalide. It is 
Habits. 
