MUSEUM OF COMPARATIVE ZOOLOGY. 141 
fine circular striations which are so characteristic of Nematodes in general. 
Here however the striations are interrupted by the median “ lines,” * 
whose smooth surface is marked off more or less regularly by deep fur- 
rows which extend transversely, yet only across the line itself. These 
lines may be seen to start near the anterior end of the body on its dorsal 
and ventral surfaces. Owing to a gradual torsion of the anterior third of 
the body, they are brought at the end of this portion into a lateral posi- 
tion, which they preserve throughout the rest of their course, i. e. up 
to a short distance from the posterior end. This apparent change in 
position is diagrammatically represented in Figure 1°. They are really 
the median lines, though their position throughout the greater part of 
the body caused them to be described at first as the lateral lines. Each 
of them is limited on either side by a narrow dark-colored border which 
under a high power resolves itself into a crowded mass of deep-seated 
dots (Fig. 7). Between these two marginal bands, on the lighter portion 
of each median line, are located in a double row the characteristic 
bristles. Their arrangement and structure will be considered later. 
It is the deep furrows in the median lines together with the dark 
borders they transsect which produce the “squares marked in outline 
by black pigment ” described by Fewkes (’83, p. 201). The transverse 
furrows appear and disappear with the movements of the animal, while 
the squares vary both in form and size (Fig. 7) and are due merely to 
the folding of the lines necessitated by the contraction of the adjacent 
muscular areas, as Bürger (91, p. 636) has shown. They have, then, 
nothing to do with internal segmentation, but are purely mechanical in 
their origin. 
The length of the males that I have examined varies from 32 to 
130 mm.? Of the seventeen which were measured exactly, only three 
were less than 55 mm, long, and the same number were over 100 mm., the 
most of the rest being close to the average, 68 mm. The diameter of 
the male varies at the head from 0.32 to 0.65 mm., at the middle from 0.4 
to 0.75 mm., and just in front of the terminal papilla from 0.2 to 0.4 mm, 
The three females caught measured 34, 38, and 40 mm. in length, and at 
the regions of the body mentioned above on the average 0.35, 0.45, and 
0.25 mm. in diameter. Thus, excepting the imperfect specimen men- 
1 The name “line” seems to be peculiarly inappropriate as a designation for 
these broad bands, but I have used it in the technical sense in which it has been 
employed for Nematodes in general. 
2 There was but one male less than 45 mm. in length, and this one must also 
have been nearly as long, since the head and a portion of the body were gone. 
