296 
COLOUR IN NATURE 
CHAP. 
PIGMENTS INTRODUCED INTO BODY CAVITY 
Situations in which in- 
Natural 
Analogues. 
Organisms. 
troduced Pigments are 
found. 
Observer. 
Polyzoa. 
In the interior of 
leucocytes which re¬ 
main within the 
zooecium. 
Harmer. 
Echino- 
In wandering cells 
Similar wander- 
Durham. 
derms. 
which may leave the 
ing cells which 
body at any point, 
contain pig- 
and which give rise 
ment, and may 
to temporary pig- 
give rise to pig- 
mentation. 
mentation. 
Dytiscns 
In amoeboid blood 
Durham. 
(Insecta). 
corpuscles which 
later formed patches 
at various points in 
the skin. 
Crustacea. 
In excretory organs. 
Cuenot. 
Conclusions 
Although certain analogies between the fate of 
introduced pigments and the natural occurrence of 
pigment in the tissues are thus rare, yet suggestions 
as to analogy have been very freely made. Eisig 
considers that the pigment which occurs somewhat 
sparingly in the skin of the Capitellidse is an effete 
product temporarily stored there, and further regards 
this as a widespread origin of pigment. Mr. Durham, 
basing his view largely on his own researches on 
Echinoderms, regards colouring - matters as either 
waste products or effete respiratory pigments which, 
when eliminated by means of amoeboid cells, may 
give rise to coloration of the skin. 
