10 
Transactions of the Society. 
some eels appear to spend their lives in harbours, etc., the yellow 
eel changes its aspect ; the dorsal colour changes from green to 
nearly black, the sides look like a freshly-coined penny with 
splendid metallic reflections, the ventral side becomes silver-white, 
and the eyes increase greatly in size. 
Now the silver eel descends the rivers and returns to the sea 
to spawn, and never returns, but we do not know if it dies directly 
after spawning or if it lives for a time. 
The silver eel, as it is called because of its ventral coloration, 
is merely the sexually mature eel, while the yellow is the sexually 
immature eel. 
It must be apparent that the sexual organs of the eel apparently 
do not attain their full development until the silver eel has entered 
the sea, though the ovaries of long silver females of 90-100 cm. 
are enormous and well over 3 cm. across. 
All the eels examined here were yellow eels, except a male, 
40 cm. long, which was nearly silver. 
These small eels were caught from June 22 to July 23 in my 
pond at Blackmore Park, which is situated about three miles from 
the Severn at Upton, and lies between Worcester and Great 
Malvern. All were caught with worm, and the larger ones were 
mostly captured at night by means of some very primitive night- 
lines. 
The pond is about an acre, divided into two halves by water- 
falls, with a small island in the centre, and very full of weed. The 
pond communicates with the Severn by a stream. 
I examined the contents of the stomach of all, and they were 
usually remains of insects ; occasionally I found fresh- water snails 
as well. 
Besides eel the pond contained roach and perch, but I never 
found any remains of these in the stomachs of the eels, nor did I 
find any of their smaller brethren^ as in some other places. 
The eel is most voracious, and seems to have great digestive 
powers. I have often found up to ten small crabs or some thirty 
prawns in stomachs of eels caught in estuaries, etc. Sometimes a 
cannibal had swallowed one of his smaller brethren of such a size 
that the tail protruded from the mouth, and they were always 
swallowed head foremost. 
The most curious find was at Valencia (Spain) where I found in 
the stomach of an eel, some 40 cm. long, a sparrow swallowed whole. 
No doubt the bird had died and somehow got into the lagoon. 
1 have seen eels caught in swamps gorged with mosquito larvae, 
and perhaps eels might be useful in the fight against malaria. In 
Majorca, where the inhabitants depend chiefly on rain-water for 
drinking as well as for household use, a few eels are generally put 
into the cisterns to keep the water pure ! At least they destroy 
some mosquito larvae. 
