Sept., 1892. colours and coloration in animals. 
201 
Among various other difficulties to the theory, the follow¬ 
ing may be mentioned. In the first place, there are cases of 
animals being provided with weapons of offence, which, 
however, are not advertised by warning colours ; for instance, 
the larva of a North American Swallow-tail butterfly is con¬ 
spicuously coloured, and possesses “ osmateria,” that is, 
glands which secrete an offensively smelling substance; 
according to the theory they are advertised by the bright 
colours. In England, the larva of the Swallow-tail has the 
organs of offence, but is protectively coloured, whereas we 
should of course expect it to have warning coloration. 
In other cases there is bright coloration, which apparently 
is not of much use ; for instance, some poisonous snakes are 
most brilliantly coloured; the deadly Elaps is an often quoted 
example, with its rings of black and red. Here at first sight 
is an excellent proof of the theory; on further considera¬ 
tion, however, difficulties crop up, for the enemies of snakes, 
if few, yet are most formidable, for they seem able to dis¬ 
regard the poison of the latter and attack them without fear, 
Hence, the bright colours seem to be of no use, if not actually 
disadvantageous, while protective coloration would appear 
to be needed, an opinion supported by the very fact that 
poisonous snakes generally harmonise with their environment. 
There is another type of these sematic colours, in which 
certain parts of the body, not of prime importance to life, are 
brightly coloured, in order, it is said, to attract the attention 
of foes to them and so protect other more vital regions ; such 
are the eyes on the wings of butterflies and the bright-coloured 
under-wings of certain moths having dusky upper wings. 
This, however, Mr. Beddard points out, cannot be the 
object of all such markings, for in the “ John Dory ” there is 
a pair of curious marks on each side of the body, which lie 
over such vital organs that a bite there would inflict serious 
injury on the fish. 
In relation to this subject of warning coloration, one of 
the novelties of the book to general readers will be Dr. Eisig's 
theory, which was published in his monograph on a group of 
the annelids, Die Capitelliden. Briefly it is as follows : — 
(1.) Pigment in the skin has in some cases been actually 
proved to be excreted matter ; it may be so in other cases 
where there is at present no direct evidence. 
(2.) In earlier times when there were no birds (the chief 
enemies of larvie) brilliant coloration due to abundant and 
varied pigment would be the rule. 
(3.) This pigment is possibly the cause of distastefulness. 
(4.) If so, brilliant colours are the cause and not the 
result of inedibility. 
