ESSEX BIRD-MIGRATION. 123
Fig. 2. Anterior half of the same specimen showing further
development of the anterior zoosporangium. x
2500.
Fig. 3. Case of the zoosporangium after liberation of all but one
of the zoospores. x 2500.
Fig. 4. A zoospore showing retractile globule and a dark
granule. x 2500.
Lettering.
e Eyespot p Pyrenoid
f Flagellum s Zoosporangium
h Hyphal thread z Zoospore
n Nucleus.
ESSEX BIRD-MIGRATION.
by william e. glegg, f.z.s., m.b.o.u.
(Being a Presidential Address to the Club).
[Read 28th March, 1936.]
PHENOMENA which cannot be seen and have to be
imagined from descriptions present greater difficulties
to the human comprehension than those which may be readily
witnessed. For this reason the nature and magnitude of the
migrations of birds are in a large measure overlooked. The
purpose of this address is to bring to our minds, so far as it can
be accomplished on paper, some idea of those movements of
birds which may be said to have some influence on and relation
to the bird-life of the county of Essex.
It may be well before coming to close quarters with the
essential part of our subject to consider in the first place the main
features of the world's bird-migration and then those movements
which are of special significance to the British Isles. By this
means a final consideration of our own county will be simplified.
Although today much remains obscure regarding migration, yet
it is clear that thousands of years ago writers knew of its exis-
tence. Dr. Eagle Clarke gives examples from some of the
early writers. One of the very earliest references to the migration
of birds is to be found in the Book of Job (xxxix, 26), where we
read "Doth the hawk fly by thy wisdom and stretch her wings
B