which the histological investigations of H.
Credner have revealed. The skull is well ossified and contains a greater
number of bones than occur in any other living Batrachian. There is
therefore strong reason for tracing the Caecilians directly from the
Stegocephalia, as was the view of T.H. Huxley and of R. Wiedersheim, since
supported by H. Gadow and by J.S. Kingsley. E.D. Cope had advocated the
abolition of the order Apoda and the incorporation of the Caecilians among
the Urodela or Caudata in the vicinity of the Amphiumidae, of which he
regarded them as further degraded descendants; and this opinion, which was
supported by very feeble and partly erroneous arguments, has unfortunately
received the support of the two great authorities, P. and F. Sarasin, to
whom we are indebted for our first information on the breeding habits and
development of these Batrachians.

The knowledge of species of Caecilians has made rapid progress, and we are
now acquainted with about fifty, which are referred to twenty-one genera.
The principal characters on which these genera are founded reside in the
presence or absence of scales, the presence or absence of eyes, the
presence of one or of two series of teeth in the lower jaw, the structure
of the tentacle (representing the so-called "balancers" of Urodele larvae)
on the side of the snout, and the presence or absence of a vacuity between
the parietal and squamosal bones of the skull. Of these twenty-one genera
six are peculiar to tropical Africa, one to the Seychelles, four to
south-eastern Asia, eight to Central and South America, one occurs in both
continental Africa and the Seychelles, and one is common to Africa and
South America.

These Batrachians are found in damp situations, usually in soft mud. The
complete development of _Ichthyophis glutinosus_ has been observed in
Ceylon by P. and F. Sarasin. The eggs, forming a rosary-like string, are
very large, and deposited in a burrow near the water. The female protects
them by coiling herself round the egg-mass, which the young do not leave
till after the loss of the very large external gills (one on each side);
they then lead an aquatic life, and are provided with an opening, or
spiraculum, on each side of the neck. In these larvae the head is
fish-like, provided with much-developed labial lobes, with the eyes much
more distinct than in the perfect animal; the tail, which is quite
rudimentary in all Caecilians, is very distinct, strong