18 NEMERTINES OF PLYMOUTH SOUND. 
This species lives under the same conditions as the other members 
of the genus, and is found associated with them among weeds between 
tide-marks and on stones dredged in 20 fathoms. 
The greater number of specimens are various shades of yellow, but 
a bright green variety is found in the coralline pools of Bovisand 
Bay. It is this variety which I think Joubin describes as 7. diadema. 
The green specimens are the longest of this species I have yet met 
with, commonly reaching 3 cm. inlength. The pigment patch is dark 
brown and quadrangular in shape, with a slight tendency to concavity 
in front and convexity behind. ‘There are three pronounced patches 
of white, two in front of the dark patch, one on each side of the head 
and somewhat triangular in outline, and one behind it stretching 
across the breadth of the posterior part of the head. I have not 
determined whether the white patches are pigment patches, or 
whether they are due to the aggregation of fatty particles, as 
Hubrecht suggests. The eyes are approximately of the same size, 
and are very distinct, the anterior pair being situated just in front 
of the dark patch, within which, however, they are in some specimens 
included. 
Many specimens of the yellow variety are met with agreeing 
generally with the above, the majority not reaching more than 15 mm. 
in length (though a single specimen was found as long as 4 em.), 
and exhibiting great inconstancy in the amount and distribution of 
the white patches, which are sometimes absent altogether, as well as 
in the size and intensity of the dark patch. 
A common variety is that in which the pigment patch is repre- 
sented by a sprinkling of brown granules over a roughly quadri- 
lateral area situated between the two pairs of eyes. Before this 
pigment are two small white patches, and behind is a transverse 
white patch, behind which again the posterior eyes are placed. In this 
variety the white granules which exist, distributed irregularly over 
the body of most specimens, become regularly arranged along the 
median line, forming a series of disconnected transverse bars passing 
from the posterior white patch on the head to the fan, composed of 
radiating white lines, which is found at the tail of nearly all the 
yellow varieties. In one specimen I have met with a still further 
stage of this tendency for the white particles to aggregate along the 
median line. In this, which had the broad dark patch of the type 
form, in front of and behind which some white granules were scattered, 
there was a very definite and conspicuous thin white median line 
passing from just behind the posterior eyes to the tail. 
In many, if not most specimens with a broad, well-defined, dark 
pigment patch on the head, those portions of the pigment which are 
situated in the line uniting the anterior and posterior eyes are con- 
