Whereas in the Cape species embryos in the same uterus are all practically of the same age (except in the month of April, when two broods overlap in P. capensis), and birth takes place at a fixed season; in the Neotropical species the uterus, which is always pregnant, contains embryos of different ages, and births probably take place all the year round.
In all species of Peripatus the young are fully formed at birth, and differ from the adults only in size and colour.
ANATOMY
The Alimentary Canal (Fig. 8).
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 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).