lower stem and spread out like the
wires of an umbrella, so as to bring all the flowers in the same head
(UMBEL) nearly to the same level. (Examples, parsley and carrot.)

UNGULATA.--Hoofed quadrupeds.

UNICELLULAR.--Consisting of a single cell.

VASCULAR.--Containing blood-vessels.

VERMIFORM.--Like a worm.

VERTEBRATA or VERTEBRATE ANIMALS.--The highest division of the animal
kingdom, so called from the presence in most cases of a backbone
composed of numerous joints or VERTEBRAE, which constitutes the centre
of the skeleton and at the same time supports and protects the central
parts of the nervous system.

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 thicke