WHORLS.--The circles or spiral lines in which the parts of plants are
arranged upon the axis of growth.
WORKERS.--See neuters.
ZOEA-STAGE.--The earliest stage in the development of many of the higher
Crustacea, so called from the name of ZOEA applied to these young animals
when they were supposed to constitute a peculiar genus.
ZOOIDS.--In many of the lower animals (such as the Corals, Medusae, etc.)
reproduction takes place in two ways, namely, by means of eggs and by a
process of budding with or without separation from the parent of the
product of the latter, which is often very different from that of the egg.
The individuality of the species is represented by the whole of the form
produced between two sexual reproductions; and these forms, which are
apparently individual animals, have been called ZOOIDE.
INDEX.
Aberrant groups
Abyssinia, plants of
Acclimatisation
Adoxa
Affinities of extinct species
--of organic beings
Agassiz on Amblyopsis
--on groups of species suddenly appearing
--on prophetic forms
--on embryological succession
--on the Glacial period
--on embryological characters
--on the latest tertiary forms
--on parallelism of embryological development and geological succession
--Alex., on pedicellariae
Algae of New Zealand
Alligators, males, fighting
Alternate generations
Amblyopsis, blind fish
America, North, productions allied to those of Europe
--boulders and glaciers of
--South, no modern formations on west coast
Ammonites, sudden extinction of
Anagallis, sterility of
Analogy of variations
Andaman Islands inhabited by a toad
Ancylus
Animals, not domesticated from being variable
--domestic; descended from several stocks
--acclimatisation of
Animals of Australia
--with thicker fur in cold climates
--blind, in caves
--extinct, of Australia
Anomma
Antarctic islands, ancient flora of
Antechinus
Ants attending aphides
--slave-making instinct
--neuters, structure of
Apes, not having acquired intellectual powers
Aphides attended by ants
Aphis, development of
Apteryx
Arab horses
Aralo-Caspian Sea
Archeopteryx
Archiac, M.
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