POLYCMTA—BENHAM. 
37 
In one case the belly is nearly as deeply pigmented blue as the dorsum; but 
this is very exceptional, as the ventral surface is generally without pigment. 
There seems to be no very definite correlation between the colouration and the 
depth at which the worms were found, for in sorting out the specimens from the jars 
in which they reached me, I rather naturally separated out those in which the colours 
were strikingly different, under the impression that I had to deal with distinct species. 
Thus, in one lot from 25 fathoms, I find four different plans of colouration or, as I sup¬ 
posed, four different species. 
Nevertheless, after tabulating the worms under their colours and their depths, 
it seems that there is a rough correlation between them. Thus, in shallow water, 
from the shore line down to 60 fathoms, the general tone of colour of the elytra is darker 
and variegated in brown, while the dorsum is without pigment, or has pale trans¬ 
verse lines of brown. The elytra, too, are more firmly attached to the elytrophores 
than in other cases. 
But in those worms that come from greater depths, say, 110-400 fathoms, the 
elytra are paler and more uniformly coloured, and may even be colourless and trans¬ 
lucent; and they are readily deciduous. On the other hand, the dorsum is now 
pigmented more deeply or more extensively, and it is from these depths that the 
handsome dark blue and violet worms were obtained. But this applies only to the 
larger specimens. 
The smaller worms are apparently less affected by depth ; or it may be that 
the change in the amount of pigment is a measure of age, for in a general way the smaller 
individuals are deeply coloured, while the larger ones, above 60 mm. in length, have 
pale or colourless elytra, with a more deeply pigmented dorsum. The smaller worms, 
from 10-30 mm. are generally found in less deep water than those from 40-90 mm. 
The texture and ornamentation also of the elytra present considerable range of 
variation, for in some the surface appears under a lens to be smooth, whereas in the 
more typical forms there is a row of pale conical tubercles along the posterior border, 
as shown in Willey’s figure 2, pi. XLI. These are usually better developed on the 
elytra from the hinder region of the body, while the more anterior ones may be without 
them. Again the entire surface may be covered with small cones, visible under a lens, 
and giving them a rough appearance to the naked eye. The marginal fringe may be 
present or absent. 
The prostomium is usually white, whether the dorsum of the body is pigmented 
or not, but in one case at least, it is marked transversely by a narrow band of brownish 
pigment (as in var. lagiscoides , as figured by Gravier (1911), pi. VI, fig. 64). The 
peristomial cirri, anal cirri, and dorsal cirri are brownish. 
In spite of these variations in colour there are two features in the distribution 
of pigment that appear to be constant, namely :—(1) the dark greyish-blue tint on the 
