MUSEUM OF COMPAEATIVE ZOOLOGY. 141 



fine circular striations which are so characteristic of I^ematodes 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 Burger ('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 

 tliese broad bands, but I have used it in the technical sense in which it has been 

 employed for Nematodes in general. 



- 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. 



