124 
STRUCTURE OP RADIATA. 
mals; and it is only in a few that even these imperfect eyes 
can he discovered. In the inferior Badiata, not the slightest 
Fig. 65.—Shell of Star Fish. 
traces of a nervous system have yet been discovered; and 
it is very doubtful whether any such structure exists in 
them. It is only among the higher 
Badiata that any locomotive power 
exists ; and this is usually so feeble 
that the animals remain in the same 
locality during the greater portion 
of their lives. Generally speaking, 
there is a period in the history of 
each species, in which there is a 
more active movement, that serves 
to prevent the accumulation of indi¬ 
viduals in one spot; but this move¬ 
ment is of a purely automatic 
character, rather resembling that of the “ zoospores ” of plants, 
than the intentional change of place of the higher animals. 
Fig. 66 .—Nervous System 
of Star Fish. 
