ge; or they may even hatch within the oviduct. This
occurs with some chameleons and some lizards, e.g. the slow-worm. The
common English lizard is also viviparous. Normally the young leaves the
egg immediately after its extrusion, but if by any chance this extrusion
is delayed they escape while yet in the oviduct.

The majority of the snakes lay eggs, but most of the vipers and the
aquatic snakes are viviparous, as also are a few terrestrial species.
The shell of the egg is always soft and parchment-like. As a rule the
number of eggs produced among the snakes is not large, twenty or thirty
being common, but some species of python lay as many as a hundred.
Generally, among the oviparous snakes the eggs are buried, but some
species of boas jealously guard them, enclosing them within the coils of
the body.

_Eggs of Amphibia._--Among the amphibia a greater variety obtains in the
matter of the investment of the egg, as well as in the number, size and
method of their disposal. The outer covering is formed by a toughening
of the surface of a thick gelatinous coat which surrounds the essential
parts of the egg. This coat in many species of salamander--using this
name in the wide sense--is produced into threads which serve either to
anchor the eggs singly or to bind them together in bunches.

Viviparity occurs both among the limbless and the tailed Amphibia, the
eggs hatching before they leave the oviduct or immediately after
extrusion. The number of young so produced is generally not large, but
the common salamander (_Salamandra maculosa_) may produce as many as
fifty at a birth, though fifteen is the more normal figure. When the
higher number is reached the young are relatively small and weak.

As a rule among the Amphibia the young leave the egg in the form of
larvae, generally known as "tadpoles"; but many species produce eggs
containing a sufficient amount of food material to enable the whole of
the larval phase to be completed before hatching.

Among the tailless Amphibia (frogs and toads) there are wide differences
in the number of eggs produced, while the methods by which these eggs
are disposed of present a marvellous variety.

As a rule vast quantities of eggs are shed by the female into the water
in the form of "spawn." In the common toad as many as 7000 eggs may be
extruded at a time. These leave the body in the form of two long
strings--one from each oviduct--of translucent globules, gelatinous in
texture,