1913] 
Pearse: Fauna of the Rock Beaches 
23 
The variations in the zones might be dwelt upon at some length, 
but it is perhaps sufficient to point out that the tension is so great 
that every variation causes a ready adjustment. 
7. Characteristics of the Fauna of the Rock Beaches 
Probably no other animal habitat is subject to such a wide 
range of fluctuations in environmental conditions as the rock 
beaches along the ocean. The flora and fauna must endure the 
Fig. 18. Shows the Effect of Exposure to the Open Sea. 
The picture is of the back of a rock-wall that ran parallel with the shore. 
The Ascophyllum hanging through a crevice from the exposed side of the 
wall is above the upper limit of the barnacles on the side away from the 
ocean. Proximity to the ocean permits organisms to climb higher on the 
rocks. 
frigid span of winter and the blistering sun of summer. There 
is no escape, the tide keeps up its eternal rhythm and the organ- 
isms are left exposed to the elements every time the water recedes. 
The exposure of the hard substratum to sun, wind, and wave has 
developed a fauna which consists largely of animals that are: 
(1) attached permanently or have well developed clinging organs; 
