Postelsia 
to 
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tion as do the concretions. Others, in regions 
that apparently have been subjected for a longer 
time to wave action, contain no such boulders. 
According to their location, illumination, 
and other factors to which forms must adapt 
themselves, the pools contain various plant and 
animal forms. 
In the pools with overhanging edges, eel- 
grass occurs in great abundance, the rock layers 
forming a point of attachment for the holdfast. 
Those pools exposed to the lower tides, and 
the best conditions of illumination and temper- 
ature, exhibit the greatest variety and number 
of life forms. 
Generally, though not always, the greatest 
variety and number occur in the largest pools. 
Im@one pool 3 <2 x 25 feet were found the 
following animal forms: mussels, goose-neck 
barnacles, acorn barnacles, chitons, lmpets, 
sea-robins, sea-urchins, sea-anemones, snails, 
and hermit crabs. The chitons and the sea- 
robins exhibited protective coloration, assuming 
the color of the rocks, which varies from dark 
rea, £0, light pink and (green;  Whese colors 
are due to incrusting alge. 
