98
THE B'IOLOGY OF FISHES
;
ownspecic balance
Which is'inherited. But
the early larvæ haVe still to]go thr0ugh the
‘
and “an" interesting suggestion has been put forward by
Bethe (1894), which goes far to explain why the develop—
ment of the Teleost is such a complicated matter. He
'
points out that the labyrinth of the statocyst or
“ hearing
”
organ is very slow in forming, and until that occurs the larva
has, so to speak, but little control over its movements.
,
The
time of development of this organ may possibly serve as an
index of the progress and differentiation of shes. The
‘
Herring, for example, has no lateral line system on the body
and the labyrinth is not linked up with the air-bladder until
'
some eight to ten weeks :after the larva is hatehéd. The
young from demersal eggs, on the other hand, seem to have
'
a well—developed labyrinth on hatehing.
,
_
-
:By Constructing a series of models in the shape of a
sh, H0ussay (1912) has studied the various ways in which
_
moves through the water-. He found it by no means
an easy matter to get any of them to travel Without wobbling
für
from side to Side, even though made f"quite
.
After- many tests and failures he suoeeeded
in making seVeral which he’=c0uld pull through the“awater at
varying speeds in a .Îfairly Straight line. From these
experiments he:caäme to—thdConclusion, that the pressure
of
the water against a moVirig exible bbdy'èpuld aceount for
all
charaÇter$sof the *shès; "
'
_}Pressure" is the
factor _in indùlding
,_
:
a1id.H0ussàÿfSwork is of great value in
‘
[
_
the 'Sh
how the
_
Ïî
in
Î
the shape;
movmg body,
ï
after}
the sh itself
_
'
has
and—has —beeniiobliged
,_
j
_
'
itSelf.
‘
Hàd 1t been
_
_
mOVingani1nal,the
_
‘A 'biologioal.Âsummar—y
form. and :
.
structuré would£appeaas“follows :— … .Æ
,
__
?
First
very