IX 
THE MARKINGS OF ORGANISMS 
197 
one region of the corolla, and are associated with 
irregularity of parts. This is well seen in the mark¬ 
ings of orchids, of the foxglove, of pentstemon, and 
many others, in which cases the parts of the corolla 
are irregular, and the markings are confined to certain 
of them. In general, in flowers the markings tend 
to be similar in homologous parts, but variations in 
the structure of homologous parts tend to be accom¬ 
panied by variation in the colour-patterns. 
Ccelentera .—The colours of Protozoa and sponges 
are too simple to show any arrangement into patterns, 
or perhaps it would be more accurate to say that the 
structure is too simple. In any case, we do not find 
the phenomenon markedly displayed before we reach 
the Ccelentera. In them it exhibits itself with the 
same simplicity seen in plants. The organisms have 
the radial symmetry so characteristic of flowers, and 
again we find that homologous parts show similar 
colouring. One tentacle is in structure and develop¬ 
ment like another, and the colours, whether uniform 
or arranged in simple banded patterns, tend to be 
identical throughout. As we have already seen, 
structural differentiation and the development of new 
colours tend to be associated ; thus knobbed or 
capitate tentacles usually have the terminal knob of 
a different colour from the rest of the tentacle—a 
fact which may be susceptible of a simple physical 
explanation. Again, when the tentacles are greatly 
reduced in size, they may cease to behave as in¬ 
dividuals in the general colour-scheme, which has 
then as its unit groups of tentacles. This occurs in 
the giant anemones ( Discosoma ), and is of interest 
because the subordination of the individual coloured 
