424 THOS. H. MONTGOMERY jr., 
along its whole extent, the latter placed between the fibre mass and 
the hypodermis. The posterior ends of these nerves seem to be com- 
posed of chromophilic without any chromophobic nerve fibres; it is 
these chromophilic nerve fibres which constitute the thin plate of 
nervous tissue at the posterior end of the caudal lobe (close to the 
hypodermis, Fig. 43 Chl.F). The hypodermis of the median side of 
each tail lobe is much thickened (Hyp Fig. 43, Pl. 39; Figs. 46, 47, 
Pl. 40; Fig. 85, Pl. 43), just outside of the nerve (Cd. NV), and there 
consists of two kinds of cells. 1) Cuticular hypodermal cells of long 
- cylindrical shape with large oval nuclei (Hyp.N) and rather well 
defined cell boundaries; these are probably sensory in function, since 
chromophilic nerve fibres (Chl. F') pass into (or between) these cells 
from the nerve, and apparently without producing plexuses there 
2) Cells (Sen. C Figs. 43, 47) with much smaller, rounded, pale-staining 
nuclei, the nucleus forming a middle dilatation in the generally spindle- 
shaped cell body. The proximal end of the cell (the end nearest the 
inner surface of the hypodermis) contains a deep-staining fibre, which 
in favorably situated cells may be traced into the nervous mass 
beneath the hypodermis; each such fibre appears usually to terminate 
within the cell against the proximal side of the nucleus, ending either 
in a loop or in a thickening. Such cells are most numerous at the 
posterior end of the tail lobe (Fig. 43), where the heightened hypo- 
‘dermis is also of the greatest extent (bounding the whole median and 
ventral aspect of the lobe); and over all this portion of the hypo- 
dermis the cuticula is tuberculated and lacks the areolar layer. These 
cells are thus very similar to the retinal cells of the eye, in con- 
taining an intra-cellular fibre which passes into the nervous system; 
such cells are probably sensory, and their fibres may be considered 
nervous in function. 
Thus the chromophilic nerve fibres of the caudal nerves terminate 
within the hypodermis, and sensory cells of the latter send their fibres 
inwards into the nerves. The terminations of the chromophobic fibres 
could not be determined, though bundles of such fibres (Chb. N Fig. 43, 
Pl. 39) may be traced along the inner surface of the hypodermis nearly 
to the posterior ends of the tail lobes; probably they innervate the 
musculature. 
The fibres of the chromophilic nerve cells could in no case be 
followed into the cuticula, nor to the branched roots of the cuticular 
tubercles. 
Just anterior to the cloacal aperture the neural lamella of the 
