THE NEMERTINES OF MILLPORT AND ITS VICINITY. 21 
the level of the posterior eyes; thence they incline obliquely backwards on the dorsal 
surface, passing just in front of the eyes and nearly meeting in the middle line; on the 
ventral surface they are continued obliquely forwards for some distance from the 
margin. 
The basis of the stylet is, according to Btreer, constricted, the constriction being 
situated, according to the figure (3), nearer the posterior end; the anterior swelling is 
as thick as the posterior; the basis is longer than the stylet. I find the basis elongated 
in shape, rounded and expanded posteriorly (v. fig. 15), and slightly longer than the 
projecting part of the stylet. There may be an appearance of a slight constriction 
around the middle of the basis, but this is due to the bulging of the posterior end; and 
an actual constriction does not exist, or is of the very slightest, the sides of the 
anterior part of the basis being parallel to each other. 
There are two reserve sacs, with two, three, or four reserve stylets in each; in one 
case there was only one reserve stylet on one side, two on the other. BUrcEr, at 
Naples, found two; in the Zzerrevch he gives two or three as the number. 
That this is the form commonly known as Tetrastemma candidum there can, I think, 
be no doubt. The only form with which it could be confused would be the nearly 
related Prostoma (Tetrastemma) flavidum, but the colours are distinctive—yellow and 
green for candidum, pink for flavidum. Again, the head is wider than the body in 
candidum, as generally in my specimens; and the white grains between the anterior 
eyes, described by MacInrosu, were also seen in some of the Millport forms. 
It may be noticed here, again, how considerably BURGER’s Naples specimens diverge 
from the description here given. In the length, in the broadening of the head, and in 
the position of the cephalic groove on the dorsum, the two correspond ; and in colour 
BourGer’s specimens—of a light or dark green, with yellow margins and yellow head 
—agree in a general way with MacInrosun’s description, if not with mine. But, on the 
other hand, BUrcEr found no pigment spots or streaks on the head, the eyes were “‘ very 
small,” and his description of the basis of the pedestal is quite different from that 
given above. In the Zverreich we find certain of these variations given as parts of the 
specific diagnosis; thus, the length is limited to 10-12 mm. (though MaclIyrosu had 
previously given 1-1} inches), the eyes are stated to be very small, the pedestal to be 
moderately constricted, and the number of reserve stylets is limited to two or three. 
A revision of the definition would therefore seem to be advisable. 
On the Distinction of P. candidum from P. flavidum. 
If the descriptions of the above two forms, as given by MacIyrosu, Jousrn, and 
BurcER in his Naples monograph, as well as the diagnoses of the latter author in the 
Tierreich, be compared, it will be found that a number of characters are given by each 
author which might serve to distinguish the two forms from each other. But, on a closer 
examination, it will appear that the points of difference are differently stated by the 
