The Cambridge natural history, Vol. 05 (of 10)Sedgwick, Adam
Science
The Cambridge natural history, Vol. 05 (of 10)
Sedgwick, Adam
Animals
[Illustration: FIG. 8.—_Peripatus capensis_ dissected so as to show the
alimentary canal, slime glands, and salivary glands. (After Balfour.) The
dissection is viewed from the ventral side, and the lips (_L_) have been
cut through in the middle line behind and pulled outwards so as to expose
the jaws (_j_), which have been turned outwards, and the tongue (_T_)
bearing a median row of chitinous teeth, which branches behind into two.
The muscular pharynx, extending back into the space between the first and
second pairs of legs, is followed by a short tubular oesophagus. The latter
opens into the large stomach with plicated walls, extending almost to the
hind end of the animal. The stomach at its point of junction with the
rectum presents an S-shaped ventro-dorsal curve. _A_, Anus; _at_, antenna;
_F.1_, _F.2_, first and second feet; _j_, jaws; _L_, lips; _oe_,
oesophagus; _or.p_, oral papilla; _ph_, pharynx; _R_, rectum; _s.d_,
salivary duct; _s.g_, salivary gland; _sl.d_, slime reservoir; _sl.g_,
portion of tubules of slime gland; _st_, stomach; _T_, tongue in roof of
mouth.]
The buccal cavity, as explained above, is a secondary formation around the
true mouth, which is at its dorsal posterior end. It contains the tongue
and the jaws, which have already been described, and into the hind end of
it there opens ventrally by a median opening the salivary glands (_s.g_).
The mouth leads into a muscular pharynx (_ph_), which is connected by a
short oesophagus (_oe_) with a stomach (_st_). The stomach forms by far the
{12}largest part of the alimentary canal. It is a dilated soft-walled tube,
and leads behind into the short narrow rectum (_R_), which opens at the
anus. There are no glands opening into the alimentary canal.
NERVOUS SYSTEM.
The central nervous system consists of a pair of supra-oesophageal ganglia
united in the middle line, and of a pair of widely divaricated ventral
cords, continuous in front with the supra-oesophageal ganglia (Fig. 9).
The ventral cords at first sight appear to be without ganglionic
thickenings, but on more careful examination they are found to be enlarged
at each pair of legs (Fig. 9). These enlargements may be regarded as
imperfect ganglia. There are, therefore, as many pairs of ganglia as there
are pairs of legs. There is in addition a ganglionic enlargement at the
commencement of the oesophageal commissures, where the nerves to the oral
papillae are given off (Fig. 9, _or.g_).
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