THE COCKLE 39 



PLATE XIII 



THE COCKLE (3) 



This is one of the very commonest of all the 

 creatures of the sea-shore, and you may find its 

 heart-shaped shells lying about on the beach in 

 hundreds and thousands. In many places, in- 

 deed, cockle-shells are found in such wonderful 

 numbers that they are crushed up and used for 

 covering pathways instead of gravel. 



Yet you may wander about on the shore day 

 after day for weeks together and never see a 

 living cockle. How is this? 



Well, the reason is that cockles live buried 

 underneath the sand. If you go down near the 

 edge of the waves when the tide is quite low, and 

 just stand still for a minute or two and watch, you 

 are almost sure to see first one little jet of water, 

 and then another, and then another, come squirt- 

 ing up out of the sand into the air. Now these 

 little jets of water are thrown up by cockles 

 which are lying buried in the wet sandy mud 

 below. For every now and then these creatures 

 draw down a little water into their gills, through 

 one of their siphon tubes, and when they have 

 sucked all the air out of it they squirt it up 

 again through the other. 



Would you like to dig one of them up and look 

 at it? Well, just take a wooden spade and try. 



