very different groups, which are mimicked by others, also
tend to resemble each other, the likeness being often remarkably exact.
These resemblances were not explained by his theory of mimicry, and he
could only suppose that they had been produced by the direct influence
of a common environment. The problem was solved in 1879 by Fritz Muller
(see _Proc. Ent. Soc. Lond._, 1879, p. xx.), who suggested that life is
saved by this resemblance between warning colours, inasmuch as the
education of young inexperienced enemies is facilitated. Each species
which falls into a group with common warning (_synaposematic_) colours
contributes to save the lives of the other members. It is sufficiently
obvious that the amount of learning and remembering, and consequently of
injury and loss of life involved in the process, are reduced when many
species in one place possess the same aposematic colouring, instead of
each exhibiting a different "danger-signal." These resemblances are
often described as "Mullerian mimicry," as distinguished from true or
"Batesian mimicry" described in the next section. Similar synaposematic
resemblances between the specially protected groups of butterflies were
afterwards shown to exist in tropical Asia, the East Indian Islands and
Polynesia by F. Moore (_Proc. Zool. Soc._, 1883, p. 201), and in Africa
by E. B. Poulton (_Report Brit. Assoc._, 1897, p. 688). R. Meldola
(_Ann. and Mag. Nat. Hist._ x., 1882, p. 417) first pointed out and
explained in the same manner the remarkable general uniformity of colour
and pattern which runs through so many species of each of the
distasteful groups of butterflies; while, still later, Poulton (_Proc.
Zool. Soc._, 1887, p. 191) similarly extended the interpretation to the
synaposematic resemblances between animals of all kinds in the same
country. Thus, for example, longitudinal or circular bands of the same
strongly contrasted colours are found in species of many groups with
distant affinities.

Certain animals, especially the Crustacea, make use of the special
defence and warning colours of other animals. Thus the English
hermit-crab, _Pagurus Bernhardus_, commonly carries the sea-anemone,
_Sagartia parasitica_, on its shell; while another English species,
_Pagurus Prideauxii_, inhabits a shell which is invariably clothed by
the flattened _Adamsia palliata_.

The white patch near the tail which is frequently seen in the gregarious
Ungulates, and is often rendered consp