DISTRIBUTION OF ANIMALS AND PLANTS IN FELSTEAD, ESSEX. 193
of the Trout. Allowing this to be a reasonable solution of sudden
changes, it throws no light on such questions as the apparently
permanent distribution of different species in the different parts of
the stream. Thus, below the Walthams, Perch and Pike have been
observed for, I believe, all the years of the present century, and
many persons can speak to a number of species permanently estab-
lished there which have no representation further up stream.
Pond fish show great tenacity of life or adaptability to circum-
stances. This becomes very obvious in the event of a dry summer.
Ponds are then sometimes reduced to mud, and all traces of fish
disappear; yet, after the lapse of one or two seasons, without re-
stocking, the same kind of fish will be found in the pond as before
the drought. I have observed this to occur more than once. This
adaptability to circumstances shows itself in another way. In certain
ponds in this neighbourhood fish do not attain their average size, but
(probably from insufficient food) spend their lives and reproduce
their species as dwarfs. In the case of Tench this is notorious. If
we allow the weight of that fish to be two pounds when full-grown,
we shall have to divide that weight by eight to give the maximum
weight of the largest fish in some of the Tench ponds here. It
certainly is not common in other organisms to find generation after
generation reproduced under such untoward circumstances. Experi-
ments with these Tench have shown that they are capable of con-
siderable increase in size. A number of fish were transferred to a
pond in which much phosphatic matter had accumulated. These
fish grew very fast, and attained the normal size quickly. The
experiment has been again and again repeated, with similar results.
This, I think, goes to prove that the distribution of fish in the river
is independent of lack or abundance of food.
Although there are agencies independent of artificial stocking,
by which fresh-water fish may be transferred from one pond to
another, I do not think that in this locality these extraordinary
agencies, as they may be called, are often brought into play. My
reason for making this statement will soon appear. The table on
next page represents the fish fauna of some ponds included within
a circle, with a radius of a mile, having its centre about a mile south
of Felstead Church.
This is the present distribution of fish in those ponds. It was
substantially the distribution of thirty-five years ago, as I can person-
ally testify, and I have evidence to the same effect, the result of a
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