88 LIFE AND HER CHILDREN. 
enemies than would appear at first sight. His thick 
skin contains a network of hard scales which will 
turn the edge of a knife if you try to cut it, while 
pointed spines (sfi) stand in ridges on his back, and 
on the sides of the rays, thus protecting the tube-feet. 
But the most curious weapons he possesses are a 
number of minute claws, like birds' beaks mounted 
on stalks (c, Fig. 37), which stand round his spines, 
and twist and snap continually as long as he is 
alive. The only use that has yet been found for 
these curious weapons is to clear the skin of the 
star-fish from the seaweeds and small animals which 
would certainly fix themselves on such a sluggish 
animal if they were not picked off. We shall see 
presently in the sea-urchin that they are sometimes 
very active in this work. 
And now as the star-fish plods on his way along the 
sea-bottom, thinking only of the creatures over which 
he can spread his capacious mouth, what has he to 
tell him of coming danger ? How shall he be warned 
if the shadow of an enemy is passing over him, or if 
he is venturing too rashly into the broad sunlight 
where his bright colours might attract dangerous 
attention ? If you notice any star-fish when it is 
alarmed or finds itself in strange quarters, you will 
see it curl up the tips of its rays, and there under 
the point of each ray (e, Fig. 37) may be seen with a 
magnifying glass a thick red spot seated on the ex- 
tremity of a nerve, and having in it as many as from 
100 to 200 crystal lenses surrounded by red cells.* 
Here then we have a far better eye than that which 
we found in the jelly-fish, and it is no wonder that 
* Haeckel, 1 860. 
