ILLUSTRATIONS 

 Ccelenterates Frontispiece 



FACK 



A promising spot for the naturalist 5 



Colony of barnacles living on a rock G 



Caprella; a small shore crustacean 9 



Strongylocentrotus; a sea urchin lO 



Ophiocoma; a brittle star lO 



A whelk shell covered with seaweeds, hydroids and tube- 

 building worms (found in a tide pool) II 



Pentaca; a sea cucumber I2 



Sea squirt; attached to a fragment of a clam shell (photo- 

 graph taken in the water) 13 



Seaweed debris left at the tide marks 22 



Orchestia, the sand flea . 23 



The white anemone 28 



Hole drilled in the shell of a mussel by a moon snail ... 32 



Moon snail (photograph taken in the water) 33 



Moon snail withdrawn in its shell. The dark area in the 

 opening of the shell is the operculum, or "door," which 



protects the animal from without 34 



Mussel attached to a rock 35 



Radula, or rasping organ of the moon snail (greatly en- 

 larged) 38 



Egg case of the moon snail 40 



Eggs of the moon snail (highly magnified). The individual 

 eggs can be seen as the small black bodies contained in the 



larger cells 42 



xi 



