414 THOS. H. MONTGOMERY jr., 
therefore in origin a hypodermal structure. This lamella is a thin 
vertical plate (N.L Figs. 22, 24, 25, Pl. 38; Fig. 26, Pl. 39), bounded 
on either side by parenchym cells, and containing a clear substance 
with vertical nerve fibres, at least the greater part of which come from 
cells placed in the central nervous system, and which course into the 
hypodermis. This is the only path for nerve fibres to the hypo- 
dermis. 
Horizontal longitudinal sections of the lamella close to its attach- 
ment with the hypodermis (Fig. 33, Pl. 39), show very clearly that 
the chromophilic nerve fibres (Chl. F) contained in it are not paired, 
but for the most part placed in a close row one behind the other; 
cross sections (Figs. 22, 24, 25, Pl. 38; Fig. 26, Pl. 39) sometimes 
show two nerves one on the right and on one the left, but this is 
probably due to two successive nerves being shown in the same ob- 
liquely cut section. Very frequently the nerve fibres within the lamella 
appear to be spirally twisted in their course; this might be produced 
by a shortening of the lamella, either normally or by the action of 
fixatives. 
In the head region this neural lamella is modified. In one female, 
as seen in the median reconstruction of the head (Fig. 2, Pl. 37), 
the unpaired neural lamella of the nerve cord extends forwards 
about as far as the cephalic ganglion, and there ends. In front of 
this are several slender non-connected septa (NV. Septa.), some paired 
and others unpaired, which connect the cephalic ganglion with the 
hypodermis; on the reconstruction the paired ones are represented in 
white, the unpaired ones in a dark color; and on the cross section, 
Fig. 15, Pl. 38, one of the septa of the most anterior pair is shown. 
In a male the arrangement of these septa (NV. Sept) was somewhat 
different, as shown in another median reconstruction (Fig. 3, Pl. 37), 
where the unpaired septa are shown in dark shading and the paired 
in light shading. The neural lamella is thus not a continuous median 
structure below the cephalic ganglion, as it is below the ventral nerve 
cord. This fact might indicate that the cephalic ganglion may be more 
or less segmental in its mode of origin from the hypodermis, that 
the nerve cells (neuroblasts) may delaminate from the hypodermis at 
several points instead of along one continuous line. But it is more 
probable that the interruptions of the lamella are here produced ‘by 
the excessive heightening of the hypodermal cells. 
The cloacal ganglion of the female (Fig. 36, Pl. 39) lies ventrally 
and just anterior to the point of bifurcation of the lateral tail lobes; 
