IX 
WARNING COLORATION AND MIMICRY 
‘265 
3. That the imitators are always less numerous in in¬ 
dividuals. 
4. That the imitators differ from the hulk of their allies. 
5. That the imitation, however minute, is external and 
visible only, never extending to internal characters or 
to such as do not affect the external appearance. 
These five characteristic features of mimicry show us that 
it is really an exceptional form of protective resemblance. 
Different species in the same group of organisms may obtain 
protection in different ways : some by a general resemblance 
to their environment ; some by more exactly imitating the 
objects that surround them—bark, or leaf, or flower; while 
others again gain an equal protection by resembling some 
species which, from whatever cause, is almost as free from 
attack as if it were a leaf or a flower. This immunity may 
depend on its being uneatable, or dangerous, or merely strong ; 
and it is the resemblance to such creatures for the purpose 
of sharing in their safety that constitutes mimicry. 
Concluding Remarks on Warning Colours and Mimicry. 
Colours which have been acquired for the purpose of serv¬ 
ing as a warning of inedibility, or of the possession of 
dangerous offensive weapons, are probably more numerous than 
have been hitherto supposed; and, if so, we shall be able to 
explain a considerable amount of colour in nature for which 
no use has hitherto been conjectured. The brilliant and 
varied colours of sea-anemones and of many coral animals 
will probably come under this head, since we know that 
many of them possess the power of ejecting stinging threads 
from various parts of their bodies which render them quite 
uneatable to most animals. Mr. Gosse describes how, on 
putting an Anthea into a tank containing a half-grown 
bullhead (Cottus bubalis) which had not been fed for some 
time, the fish opened his mouth and sucked in the morsel, 
but instantly shot it out again. He then seized it a second 
time, and after rolling it about in his mouth for a moment 
shot it out again, and then darted away to hide himself 
in a hole. Some tropical fishes, however, of the genera 
Tetrodon, Pseudoscarus, Astracion, and a few others, seem 
