THE NEMERTINES OF MILLPORT AND ITS VICINITY. 23 
mentation of the head, the occurrence of white splashes in front of the eyes, the number 
of stylets in the reserve sacs, the shape of the head, and the disposition of the eyes, 
were all found to be variable. 
Lastly, the Millport specimens in several cases showed a combination of the characters 
of P. candidum and P. flavidum, and seem thus to have been to some extent inter- 
mediate between the two. While agreeing on the whole more closely with P. candidum, 
in one case a pinkish colour was found, pink or rose being the characteristic colour of 
flaridum. The arrangement of the eyes in a square (characteristic, according to 
MacIntosu, of candiduwm) was as a rule replaced by the arrangement in a rectangle 
(characteristic of flavidum). The head of my specimens was as a rule only slightly, 
sometimes very slightly, broader than the next succeeding part of the body—the 
condition, that is, was intermediate between those characteristic of candidum and 
flavidum respectively. And while the anterior and posterior eyes were as a rule of the 
same size, In one instance the condition of P. flavidwm was reproduced, in which form, 
according to MacInrosu, the anterior pair of eyes are larger than the posterior. 
I do not consider that any of my specimens represented the typical form of 
P. flandum ; and it would therefore be unwise in me to pronounce a definite opinion 
on the following point. But having regard to the want of any general agreement as to 
the characters by which the above two forms are to be distinguished, and, in addition, 
to the great variability of the forms themselves, as well as to the fact that forms exist 
which may be considered as intermediate in character, it seems not improbable that it 
will be found advisable to unite the two under a common designation. 
Oerstedia dorsalis (Abildg.) (= Tetrastemma dorsale). 
A single specimen was dredged in the channel near the Biological Station. 
Length one-third of an inch; comparatively stout, cylindrical or sausage-shaped, 
of generally stiff appearance ; the blunt posterior end tapers very little. The specimen 
frequently doubled itself up so that its two halves lay apposed side by side. It pro- 
truded its proboscis on apparently no provocation ; it ultimately broke into two under 
examination, and the anterior part then vomited and shook off the proboscis. 
The general colour was yellow to orange, very slightly lighter on the ventral surface ; 
a brownish pigment was also present, with a double arrangement—(i.) in three bands, 
two lateral and one mid-dorsal, not very definite; (ii.) in transverse bands over the 
dorsum, which became fairly conspicuous when the animal contracted itself, and which 
then gave the animal an annulated appearance. Scattered over the body were a number 
of minute white dots, easily seen with a low power of the binocular microscope; these 
were specially aggregated to form a mid-dorsal line, superposed on the median dorsal 
brown-pigmented streak. The animal frequently twisted itself so that the mid-dorsal 
white line appeared as a spiral round the body. 
The head was flattened, not broader than the body, not marked off, tapering some- 
