_
THE SEA BOTTOM
.
attaining to a length of a __foot and a diameter of three
inches, and has a thick brown or yellowish skin. It moves,
like its relatives the starsh, by means of ve rows —-of
tube—feet, and has the curious habit, when irtated, of
-shooting out masses of sticky white threads, Which swell
up greatly in water and completely
‘
animals.
Because of this habit, it is also called— the“,
cotton-spinner.
On
greater provocation it ejects its—_
and entire viscera, later growing a fresh set.‘
Crustaceans
are
not especially Common in, mud
number of small species are
_
.
_
_
SHALLOW WATER ZONE
'
_
Many o£ the animals just mentioned, and: also a host of
-
others, are also found in the Sub—littoral or Shallow Water
'
zone, for these two regions contain as
and varied a—
population as any on the earth’s surface. The bottom is
usually soft, of sand, m=ud or
mixed
.
with stones: and rocks which, together withhosts of emptyÏ;
shells, furnish a foundation for— the; attached animals.
We
can here only refer to a. few of the commémest or more
interesting inhabitants, some of which are: also, found in.
shaower water,‘for theboundaries we:make are
»
articial.
Carnivores and animals which feed on particles
in suspension—animate or inanimate—or swä.llow the bottom
mud- and sand, are especially— abun‘d‘antfor, though hght
_
penetrates, if the water be clear, _t_o depths of.— 100- fathoms
or even more, it:is insufcient to support plant life in depths '
considerably less: than this;
Down to
fathoms,
hOWever, there is frequently an. abundance' of the: limy_
coralline weeds or Nullipores, of-which the; comaoneät,
'
Lithothamnion, forms an important constituent of. the=sea
bottom- inmany par.—ts,
'
"
'