SWIMMING;ANIMALS
77 _
true bone is to be found in their skeletons, but that they
consist of that cùrious transparent substance known as
which, for all its delicate appearance, is in reality
'
tough.
In the bony shes on the:
skeletons are all made of true bone, which is hardîd
_
is only a further Stage in ”evolution, bone
being
which strengthening deposits .
of
been»
:>The skeletons of. very young
animals consist of cartilage,
This being the
case‘it is not surprising to nd that the cartilaginous shes
are more primitive than the bony shes,
appeared rst
in the course of evolution.
.
In the struggle for existence
during the history? of the world, however, the shes with
true bony skeletons have been by
most adaptable
.
and are now far more numerous both in _kindS and in
numbers than are the shark family; ><
-
‘
'
But this is not the place to enter into a scientic discussion on the evolution of sheSor to_describei detail all
_
the many different species of
at the present
.
day.
It is rather the
of these pages to show how
some of the various shes behave and live in nature and the
'
part they play in the world under the sea. ‘
,
'
Sp,gmmG
In dèscribing the life of any sh, it- is reasonable to begin
from the day of its birth. Most marine shes, but not
quite all, lay eggs ; only a few are viviparous, that is, are
born alive and do not hatch from an”egg previously shed
by: the mother; Amongst these few
the viviparous
'_
blenny (Zoarces), one or two kinds of dog-sh and the saw—
_
sh
(Pristis)[
-
,
—
'
—
'
»
.
»
let us consider the majority, that is the egg—laying
_
Some sh lay their eggs on the sea. bottom attached