94 
LIFE AND HER CHILDREN. 
find alive, unless by those who know their haunts 
under large stones on the sand, or who fish for them 
in deep water ; yet they are plentiful on all our 
coasts, and most people have picked up fragments of 
their shells upon the beach. When they are found, 
however, and placed in salt water, they well repay 
the trouble of a search, if only because they are so 
different from anything we have seen before. 
Imagine a hedgehog rolled up tightly into a ball 
and beginning to walk along, not on his feet, but on 
the tips of his spines as if on stilts, and putting out 
here and there long fine tubes like threads of gutta- 
percha to anchor himself on his road, and you will 
have a fair picture of a walking echinus or sea-urchin, 
as he moves slowly along an aquarium or over the 
rocks on the sea-shore. There is something singu- 
larly whimsical in the 
movement of this prickly 
ball as it gravely lifts 
some of its sucker-feet to 
plant others, guiding it- 
self the while by its 
movable spines. Each 
spine looks so knowing 4 , 
turning itself round by 
its ball-and-socket joint, 
apparently making its 
own little excursions 
without regard to what 
the other spines are doing; 
and in large specimens, 
where the little claws can be seen round the spines 
* Echinus sph&ra. 
Fig. 39- 
A. Sea- Urchin * walking on a rock. 
m, Mouth. /, Walking tubes, 
r/, Spines. 
