236 THE ESSEX NATURALIST.
in this way, but a certain number of encouraging results have
been obtained in the preliminary observations which have been
made with this microscope.
In bringing this Address to a close, I may perhaps say just
one word as to the bearing which the study of water-surface
plants and animals in their relation to the surface-film has
upon the general question of the adaptation of organisms to their
environment. It seems clear, I think, that, as is so often true
in other cases, no really new feature of a fundamental nature
has been developed by the organisms for the utilisation of the
force of surface-tension. The most important of the means
by which surface-tension is exploited is evidently the posses-
sion of some structure or exudation which is water-repellent
But, such structures and exudations had undoubtedly been
produced, probably merely as by-products of their physiological
activities, by both aquatic and terrestrial plants and animals
long ages before the present water-surface organisms took to a
life at the surface. In fact it is almost certain that it was the
possesion of some such water-repellent characters which enabled
the progenitors of the organisms now using the surface-film for
support, to make their first attempts at living at the surface.
But, although the fundamental requirement was already present,
much subsequent specialisation of the various water-repellent
characters has been required to fit the needs of each type of
organism and, as we have seen, such adaptations have been
remarkably varied while being carried in some cases to an
astonishing degree of perfection.
A few references to the literature dealing with plants and
animals in their relation to the surface-film may be added.
Brocher, F.—Les Phenomenes Capillaires—Leur importance dans la
biologie aquatique.—Annales de Biologie Lacustre, Tome IV,
1910, p. 89.
Miall, L. C.—The Surface-film of water and its relation to the life of
plants and animals.—Nature, vol. xlvi, 1892, p. 7.
-------------The Natural History of Aquatic Insects.—1895 (and 1903).
Scourfield, D. J.—Entomostraca and the Surface-film of Water.—
Journal Linnean Society—Zoology, vol. xxv., 1894, p. 1.
-------------Note on Scapholeberis mucronata and the Surface-film of Water.
—Journal Quekett Microscopical Club, Ser. 2, vol. vii., 1900, p.
309.
-------------Hydra and the Surface-film of Water.—Journal Quekett Micro-
scopical Club, Ser. 2, vol. viii., 1901, p. 137.