158
ÎTHEÇBIOLOGY OF FISHES
differentiation of the body into many va1‘ied cells led to the 1} _i _f
'
receiving and emitting functions gradually becoming
separated and conned to distinct organe and places; The Î
sensory system receives the various kind of messages, the
mbtor system, represented by the muscles and
%
developed therefrom and directed from the central control,
:_
gives the response of the organism.
:
*
…
.
:
The separation appears to be most complete in the
Higher Veftebràtes and man, and our senses only register
'
Î _;’_"_
certain kinds of power waves.
It is therefore someWhat
difcult torealise that other forms of life, and particularly
the shes, may be tuned in quite different ways.- Our
_
.
range
very restricted ;_
With0ut special appliances We
know}èortrPai*ativelylittle of the world around us; even I ÏjÏlj
as every one is aware, the senses are not
,t_Qÿÿibe
other side, our responses go almost …
thrOu‘gh the? muscular System, yet this is not the,
case-among shes, as we. have just seen. And if we close
…
our-eyes and" press-lightly on the eye—balls, the eld Of
1_
vision Within =gradually becomes lled-,with light-wavesÏ—ï
_
sudden blow
a ash, The radiant energy f0r
'
_' the
of emission is there,—but we do not know hoW to
' -‘Ÿ‘We_nse.it without knowing
,
ï
.Ï
fThe-nerv0üs
and ,
—.
stillarises from- the
-
draWa1 off—he:
ax1sm‘fethemtenorhaslcdtothe 7
-'
derelopment£o£ amostcomphcatednetwerkofcemmumca
:” 1ntheh1gheranrm3151tmay
three or more“
:..; neurones,closely1t€rhk€d together by dendrites or
branchesofthenervecell,before the response is sent to
neurone (Fig. 37). The
:}, —.mode“of transport is perhaps like that_of the low-tension
%_
.
there gmay, be movements ”of the
:—j_,
is used'in the process: = Large _;
Ë
quant1ties
hQwever,î are Ë; required, as may ; bÏè;
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