266 The N.Z. Journal of Science and Technology. [July 
of the alterations. As a matter of fact, there is a primitive colour-pattern 
in young shells which is sometimes retained in nearly adult forms. It 
consists of very faint brown divaricating lines, sometimes associated with 
broken radials but very much weaker than them. It is found both on 
depressed and conical shells. • When the “ earli ” pattern starts to 
develop, this primitive pattern disappears and there are areas of milky- 
white shell without any colour. It seems as if the “ earli ” pattern is 
merely an accentuation of the primitive pattern on a larger scale. 
I have_ been unable to connect the presence of radial or “ earli ” 
pattern with environment. Both are found on shells growing on rocks of 
the same nature, at high- and low-water mark, on clean and weed-covered 
shells, and they occur together. 
There is one observation regarding colour, however, which seems of 
some importance. The pattern lies in the outer layers of the shell and is 
often lost by corrosion. In such cases there is a patternless colour in the 
thickened inside layer of the shell—patternless because it is not deposited by 
the growing edge of the mantle. The muscle-impression becomes deepened 
in colour, and there is further colour outside it. This is true not only of 
the Cellana radians group, but also of C. ornata and C. denticulata. In 
C. stellifera, which never occurs much above low-tide mark, it is rare to 
find more than slight corrosion at the apex, but in such shells the usually 
white muscular impression becomes coloured. It would be of interest to 
know whether this phenomenon is general in limpets. Internal colour is 
frequently made a character for specific discrimination, but if it depends 
partly on corrosion it is obvious that it should not be so used without 
reference to the corrosion of the shell. The fact that corroded shells 
possess internal colour suggests that the colour is necessary to the animal 
as a protection from light or heat. Corrosion is in part due to abrasion 
by water and sand, but probably it is due in most cases to weathering. The 
shells highest up on the rocks become nearly dried during low tides and 
must be coated by a strong solution of brine, which may exercise a solvent 
action on them. They are frequently washed by rain, and alternately 
wetted and dried. Few shells in such positions are not corroded, and it 
is probable that the action of the weather is more effective than the 
abrasive action of the waves. The effect, however, is the same in both 
cases—viz., the removal of the original colour-pattern and the deposition 
of the internal colour. 
As regards colour and the nature of the rock, my observations do not 
fully bear out Iredale’s suggestions. The shells on the Bed Bocks near 
Wellington differ not at all from those on the adjacent greywacke rocks. 
In the depressed forms ( C . radians ) entire lack of colour-pattern is rare, 
and I have only obtained one specimen, from Kapiti Island, which is 
colourless when adult. 
In a series from the white Caversham sandstone cliffs of Seaview, near 
Dunedin, however, there seems to be a tendency to adaptation. A fair 
proportion of the shells are rather dark, due to crowded radial bands, 
and a still smaller proportion show a tendency to an “ earli ” pattern. 
A large number of shells, however, are of a yellow colour, with simple, 
distant dark radials. In these shells the primitive divaricating markings 
have disappeared. In the yellow colour the shells show an approach to 
C. jlava. 
C. flava I have been unable as yet to study in situ , but offer the 
following suggestion. It is common only on the east coast of the South 
