146 BULLETIN OF THE 
It is difficult to believe that this canal represents merely the central 
protoplasmic core upon which the scale was formed, since, if this were 
the case, it would be closed terminally by at least a thin layer of cutic- 
ular substance. But this is not the case. The opening is always larger 
and plainer than the canal itself, which is too narrow to be measured. 
These structures are entirely lacking in the female. Their occurrence 
in the male alone, and over only a limited area near the posterior end, 
suggests connection in some way with the sexual act. If it be the case 
here, as in Gordius, that the male grasps the female during copula- 
tion by winding itself about the posterior portion of her body, the use of 
these scales in holding on to the cuticula, which differs from that of 
Gordius in being smooth, is at once suggested. The canal may then 
be either the duct of a gland or a tactile organ. 
The cuticula of the female is nowhere more than 1 » thick, and pre- 
cludes thus any profitable study of its structure. The bristles are pres- 
ent, and do not differ materially from those of the male. They are, 
however, somewhat more slender and shorter. The scales of the male 
are entirely lacking, and no analogous structures were found. 
b. Hypodermis. 
The hypodermis, or subcuticula, as it is often called in Nematodes, 
forms immediately under the cuticula a layer of comparatively uniform 
thickness and structure, being, however, peculiarly modified in the an- 
terior chamber, in the median lines, and in the terminal organ of the 
male. Its modifications will be considered under the organs in question. 
Sometimes no trace of this layer can be found, but in the majority of 
sections it can be demonstrated in some places. 
The hypodermis (Fig. 20) normally appears as a narrow granular layer 
7 » in thickness, without cell walls, but containing numerous prominent 
nuclei arranged somewhat regularly, and characterized particularly by 
the indefinite distribution of their chromatic matter and the faint, 
uncertain way in which they are stained. It is separated from the 
underlying muscular layer by a delicate basement membrane, which 
ordinarily cannot be demonstrated, but which is easily seen where the 
muscle cells are shrunk apart or torn away. 
Median Lines. — The hypodermis appears to be highly differentiated 
in two regions, the dorsal and ventral lines, where it becomes so much 
thicker as to cut down into the muscular layer and separate it into two 
lateral areas. These lines were regarded by Verrill and Fewkes as 
lateral; but, as Biirger has clearly shown, they undoubtedly correspond 
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